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Smart Optical Catheters for Epidurals
摘要： Placing the needle inside the epidural space for locoregional anesthesia is a challenging procedure, which even today is left to the expertise of the operator. Recently, we have demonstrated that the use of optically sensorized needles significantly improves the effectiveness of this procedure. Here, we propose an optimized configuration, where the optical fiber strain sensor is directly integrated inside the epidural catheter. The new design allows the solving of the biocompatibility issues and increases the versatility of the former configuration. Through an in vivo study carried out on a porcine model, we confirm the reliability of our approach, which also opens the way to catheter monitoring during insertion inside biological spaces.
关键词： medical optics instrumentation,fiber optics sensors,clinical applications,fiber Bragg gratings
更新于2025-09-23 15:22:29
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Side chain dynamics in semiconducting polymer MEH‐PPV
摘要： The characteristic nanoscale dynamics of the alkyl side groups in the light-emitting polymer poly[2-methoxy-5-(20-ethyl-hexyloxy)-1,4-phenylene vinylene] have been investigated using quasi-elastic neutron scattering (QENS). The measurements were taken below the polymer’s glass transition (T ≤ Tg ’ 353 K), where the main backbone is in a rigid state and does not contribute to the broadening of the QENS signal. An analytical diffusion model consisting of a static term and two dynamical components, characterizing the flexible side groups, provide an excellent fit to the experimental data. The two observed dynamical processes are all localized in character, with no meaningful dependence on temperature. The faster process, with characteristic timescale of (cid:2)18 ps at room temperature (RT), can be linked to the average mobility of the terminal protons of the alkyl chain, while the slower process, with characteristic timescale of (cid:2)170 ps at RT, to those protons at the other end of the alkyl chain, closest to the backbone. While the fraction of mobile protons contributing to the QENS signal increases with increasing temperature, the characteristic timescale and confining volume within which the protons are able to move locally depend chiefly on the polymer conformational state. ? 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47394.
关键词： quasi-elastic neutron scattering,semi-conducting polymer,optical and photovoltaic applications,polymer dynamics,spectroscopy
更新于2025-09-23 15:22:29
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Cross correlation peak-seeking technique of BOTDR based on the incomplete Brillouin spectrum
摘要： Considered the limitation of sweeping frequency technique, Brillouin optical time domain reflectometer (BOTDR) can only perceive slow external interference. It greatly limits the scope of application. For perceiving rapid external interference, a method of cross correlation peak-seeking technique based on incomplete Brillouin spectrum (IBS) is proposed, and the feasibility of the method is verified under the background of the monitoring of sound barriers along the high-speed railway. The numerical simulation results indicate that the probability that obtains an accurate peak frequency error within the 0.50 MHz can reach 49/50, when frequency interval for sweeping is 5 MHz and number of splicing IBS is 80. In addition, to select the optimal parameters of the system, we also take a further analysis on the effect of the splicing times and the frequency interval for sweeping on the peak detection accuracy. This method is significant to extend the application of BOTDR from slow changing fields to rapid changing fields.
关键词： Optical time domain reflectometry,Brillouin scattering,Optical fiber measurement applications
更新于2025-09-23 15:22:29
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Yellow-emissive carbon dots with a large Stokes shift are viable fluorescent probes for detection and cellular imaging of?silver ions and glutathione
摘要： Yellow-emissive carbon dots (Y-CDs) were prepared by a solvothermal method using anhydrous citric acid and 2,3-phenazinediamine as the starting materials. The Y-CDs display a 24% fluorescence quantum yield, a 188-nm Stokes’ shift and excellent stability. They are shown here to be excellent fluorescent probes for the determination of Ag(I) ion and glutathione (GSH). If exposed to Ag(I) ions, they are bound by the carboxy groups of the Y-CDs, and this causes quenching of fluorescence (with excitation/emission maxima at 380/568 nm) via a static quenching mechanism. This effect was used to design a fluorometric assay for Ag(I). The quenched fluorescence of the Y-CDs can be restored by adding GSH due to the high affinity of GSH for Ag(I). The calibration plot for Ag(I) is linear in the 1–4 μM Ag(I) concentration range, and the limit of detection is 31 nM. The respective values for GSH are 5–32 μM, and 76 nM, respectively. The method was applied to the detection of Ag(I) in spiked environmental water samples and gave recoveries ranging from 93 to 107%. It was also applied to the determination of GSH in tomatoes and purple grapes and gave satisfactory recoveries. The Y-CDs display low cytotoxicity and were successfully used to image Ag(I) and GSH in H1299 cells.
关键词： Fluorescence microscopy,Applications,Stern-Volmer plot,Fluorescence imaging,Fluorescence detection
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Kiev (2018.4.24-2018.4.26)] 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Simulated Phantom Projections for Reconstruction Quality Control in Digital Tomosynthesis
摘要： IMASIM software was used to generate sets of X-ray projections for quality control in digital tomosynthesis. Corresponding projections of a polymethylmethacrylate(PMMA) phantom with the same size were taken using x-ray tomosynthesis imaging equipment. A specially designed fiduciary marker bead phantom was used to measure the relative positions of imaging system elements. A good correspondence was found between real and simulated projections and reconstructed slices. The ability to create simulated projections with predefined imperfections gives valuable benefits to analysis of overall tomosynthesis performance.
关键词： X-ray applications,digital X-ray tomosynthesis,quality control,biomedical imaging,numerical simulation
更新于2025-09-23 15:22:29
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Design of Microstrip Bandpass Filters Based on Stair-Step Patch Resonator
摘要： In this research article, single pole bandpass filter using stair-step patch topology based on symmetrical and asymmetrical step impedance resonators has been designed for industrial, scientific and medical (ISM) band application. This filter has been modeled by Microwave Office simulator using RT/Duroid substrate constant of 10.8, the substrate thickness of 1.27mm, loss tangent of 0.0023 and copper metallization thickness of 0.035 mm. To enhance the stopband levels of filter response, two microstrip bandpass filters have been designed as two-pole configurations based on edge, and cross-coupled stair-step patch resonators using the same simulator tool and substrate specifications. The proposed filters have compact sizes of (0.311λ(cid:2917)(cid:2925) x 0.233λ(cid:2917)(cid:2925)) for single pole filter, (0.578λ(cid:2917)(cid:2925) x 0.24λ(cid:2917)(cid:2925) )for two-pole edge coupled filter and (0.566λ(cid:2917)(cid:2925) x 0.234λ(cid:2917)(cid:2925))for two-pole cross-coupled filter designed at center frequencies of 2.4, 2.46 and 2.41 GHz respectively. These filters have interesting insertion loss and return loss magnitudes, narrow band frequency responses, second harmonic suppression and good stopband levels. Apart from ISM band applications, the proposed filters can be adopted in WLAN systems and Bluetooth applications for short range devices. The experimental results for designed filters are of good consistency with the simulations.
关键词： ISM band applications,stair-step patch resonator,filter compactness,narrow band frequency response,Microstrip bandpass filters,second harmonic frequency blocking
更新于2025-09-23 15:21:21
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Preparing Semiconducting Nanoribbons with Tunable Length and Width via Crystallization-Driven Self-Assembly of a Simple Conjugated Homopolymer
摘要： Precise control of width and length of one-dimensional (1D) semiconducting nanostructures has attracted much attention owing to its potential for optoelectronic applications. However, regulating both their length and width using conjugated polymers or even block copolymers is a huge challenge. To solve this problem, we synthesized a unique conjugated polyacetylene homopolymer by living cyclopolymerization, which spontaneously formed 1D nanoribbons via in situ nanoparticlization. Interestingly, their widths could be controlled from 8 to 41 nm, which were directly proportional to their degree of polymerization. Furthermore, a self-seeding technique via crystallization-driven self-assembly (CDSA) was used to control the length of the nanoribbons up to 5.2 μm with narrow distributions less than 1.1. Interestingly, adding a block copolymer unimer to these nanoribbons produced triblock comicelles by the living CDSA mechanism. Finally, these nanoribbons were visualized directly by super-resolution optical fluorescence microscopy. Now, one can modulate both length and width of 1D nanoribbons simultaneously.
关键词： semiconducting nanostructures,crystallization-driven self-assembly,nanoribbons,optoelectronic applications,conjugated polymers
更新于2025-09-23 15:21:21
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Axion sensor
摘要： Optical tweezers are a popular tool for manipulating and sorting individual nanoparticles. Now, Avinash Kumar and John Bechhoefer from Simon Fraser University, Canada have shown that when equipped with a suitable feedback scheme tweezers can be used to create a more complicated force field, such as single- or double-well harmonic potentials, for controlling particle dynamics. In the experiments, a polarized 532-nm laser was used for trapping and detection. The polarization of the detection beam was rotated by 90° with a half-wave plate so that a polarized beam splitter could separate the detection beam from backscattered light arising from the trapping laser. Quadrant photodiodes were used to detect the particle’s fluctuation and dynamics. Two feedback loops continuously regulated a pair of acousto-optic deflectors to compensate for any fluctuation in the total intensity. The shape of the double-well potential was reconstructed from the Boltzmann distribution of the position measurements. The well separation was 10.6 nm, which is far below the diffraction limit (≈ 220 nm). The ability to create and control energy landscapes at scales comparable to the size of proteins offers intriguing possibilities for biophysical applications.
关键词： biophysical applications,nanoparticles,optical tweezers,force field
更新于2025-09-23 15:21:21
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Beam phase retrieval based on higher order modes in cylindrical superconducting radio frequency cavities
摘要： The control of beam phase relative to the accelerating RF field within a superconducting cavity is important in many accelerator applications and is of particular importance for a free electron laser facility. As standard practice, the phase is usually inferred from the beam-induced transient field with respect to a timing reference. We report here on an alternative and novel means of beam phase determination based on beam-excited higher order electromagnetic modes and the accelerating electromagnetic mode, which are conveniently available from the same coupler. The monopole modes are immune to the electron beam offset and therefore are best suited for the task. A coupled circuit model is used to assist the development and to rapidly assess the facility of the method. Simulations based on the circuit model indicate that the resolution of this system depends critically on the signal to noise ratio. Beam-based measurements with a test setup were carried out at the European X-ray Free Electron Laser (XFEL), Germany. Based on this new method, we have routinely obtained a resolution of 0.1°. The best resolution observed with the current setup was 0.03°. These results agree very well with the predictions from those predicted by a circuit model. The system investigated here can be used to provide diagnostic information for the current low level RF system employed in the European XFEL. To this end, the associated electronics are under development. This monitor is the first of its kind that can deliver direct and online measurements of the beam phase with respect to the RF field.
关键词： higher order modes,accelerator applications,beam phase retrieval,free electron laser,superconducting radio frequency cavities
更新于2025-09-23 15:21:21
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[IEEE 2018 41st International Spring Seminar on Electronics Technology (ISSE) - Zlatibor, Serbia (2018.5.16-2018.5.20)] 2018 41st International Spring Seminar on Electronics Technology (ISSE) - Solid-Liquid Interdiffusion Bonding Based on Au-Sn Intermetallic for High Temperature Applications
摘要： This paper covers one of the aspects of solid-liquid interdiffusion (SLID) bonding of semiconductor structures to substrate for high temperature operation. Investigations were focused on Au/Sn intermetallic compounds formed at the interface between Au metallization on the chip and Sn metallization on the DBC (Direct Bonded Copper) substrate. Two version of SLID were applied: one stage process at 350?°C and two stage process short time at 280?°C + long time at 180?°C. Second process is divided into two steps: short high temperature (280?°C) step for melting Sn and initial intermetallic compound formation and long low temperature (180?°C) step for solid state diffusion process. Design of experiments technique was used for process optimization. The best process parameters were obtained and they were applied for monocrystalline GaN chips assembly to DBC substrates. In the long-term stability tests at 300?°C it was proven that both versions of investigated SLID technique can be applied for monocrystalline GaN chips assembly. Critical condition for this assembly operation is high enough pressure applied on the chip to initiate diffusion process.
关键词： High Temperature Applications,GaN chips,Au-Sn Intermetallic,DBC substrate,Solid-Liquid Interdiffusion Bonding
更新于2025-09-23 15:21:21