External Resonator Research Articles

Albumin-Based Nanotheranostic Probe with Hypoxia Alleviating Potentiates Synchronous Multimodal Imaging and Phototherapy for Glioma.

Highly infiltrative and invasive glioma cells obscure the boundary between tumor and normal brain tissue, making it extremely difficult to precisely diagnose and completely remove. The combination of multimodal imaging with effective treatments to diagnose precisely and guide surgery and therapy accurately is desperately needed for glioma in the brain. Here, we report a biomimetic catalase-integrated-albumin phototheranostic nanoprobe (ICG/AuNR@BCNP) to realize multimodal imaging, amplify phototherapy, and guide surgery for glioma after penetrating the blood-brain barrier, accumulating into deep-seated glioma via albumin-binding protein mediated transportation. The phototheranostic nanoprobe enabled fluorescence, photoacoustic, and infrared thermal imaging with desirable detecting depth and high signal-to-background ratio for clearly differentiating brain tumors from surrounding tissues. Meanwhile, the nanoprobe could effectively induce local hyperthermia and promote the level of singlet oxygen based on alleviated hypoxic glioma microenvironment by decomposing endogenous hydrogen peroxide to oxygen to amplify phototherapy. Thus, significant inhibition of glioma growth, extended survival time, alleviated tumor hypoxia, improved apoptosis, and antiangiogenesis effects were exhibited in several animal models including the periphery and the brain through intravenous or intratumoral injection, meanwhile with low toxicity to normal tissue. The phototherapy was also guided by the assistance of external bioluminescence, magnetic resonance, and positron emission tomography imaging. Moreover, the nanoprobe could accurately guide the glioma resection. These results suggest that the phototheranostic nanoprobe is a promising nanoplatform specifically for glioma to achieve multimodal diagnosis, effective phototherapy, and accurate imaging-guided surgery.

Gravitational effects and mode interactions of vertical cantilever beams

As a basic structure and a fundamental vibration issue, the vibration of cantilever structures has been thoroughly studied, and there are some generally accepted conclusions, for example, internal resonance does not take place in the transverse vibration of a basic cantilever beam. In this study, by including 3:1 internal resonance caused by gravity, mode interactions of hanging cantilever beams are firstly presented in the primary and secondary external resonance. The second mode can be easily and remarkably stimulated in the primary resonance, while the first mode response can also be generated in the secondary resonance. Besides, internal resonance complicates the dynamic characteristics of mode responses, such as ring-like and other strange response shapes, and further influences the mode interactions in the primary resonance. Furthermore, with non-strict internal resonance and large excitation amplitude, the chaotic motion can be achieved in the secondary resonance, which may not occur in the primary resonance. In summary, the research in this paper shows that, although it is a fundamental subject of vibration, there are still some unknown phenomena in the vibration of cantilever beams. Understanding these phenomena will undoubtedly help design engineering systems and control structural vibration.

A High-Power, High-Efficiency Hybrid Silicon-Based Erbium Silicate-Silicon Nitride Waveguide Laser

Silicon-based lasers have played an important role in silicon-based optoelectronic integrated system. Recent studies demonstrated erbium silicate was an ideal candidate material for high performance silicon-based lasers in the telecom wavelength due to its high erbium concentrations. In previous works erbium silicate compounds led to high waveguide losses, the hybrid layers of erbium silicate and silicon nitride seem to be suitable to overcome high losses of previous designs with Er-based gain media waveguides. So a hybrid erbium silicate-silicon nitride waveguide laser has been proposed to make up for the loss problems of erbium silicate material, and to obtain high laser output power and high efficiency. Then, different cavity geometries, including ordinary strip-loaded DFB cavity with pump/signal resonant external cavity, have been discussed and optimized to further improve the laser performance. A 70 mW high-power laser with the maximum power conversion efficiency of 60% can be obtained in a 6.5 mm distributed feedback cavity length through developing the optimized signal external resonator cavity and grating reflector. Finally, the usability of this technology has been discussed as a potential input laser for silicon photonics. The results indicate the hybrid erbium silicate-silicon nitride waveguide lasers with high performance as potential candidates for future scale integrated silicon-based lasers application.

Development of a composite polymer-dye medium for tunable laser emission

We demonstrate optically pumped laser medium with emission in the visible spectral range from binary solutions of Rhodamine 6G and Rhodamine B in epoxy resin as matrix without appending additional scattering centers. A frequency doubled Q-switched Nd: YAG laser was used for pumping. The generation’s behavior is similar to random laser (RL) with no external optical resonator. The influence of the nanostructured morphology of the medium on the laser properties was investigated by means of SEM, AFM, TEM, SAED, Spectrofluorimetry and Spectrometry. The laser emission is characterized by high intensity – energy per pulse – 300 µJ, threshold pump energy 1.7 mJ, relatively low beam divergence of 70 mrad (for RL) and spectrally narrowed major peak at 597 nm. The new gain medium was also investigated in a conventional tunable resonator. Generation with continuous tuning in the spectral range 590–610 nm was obtained. This new effective nanostructured medium, which shows with high optical and energy parameters, can be used in speckle-free laser imaging, time-resolved microscopy, high speed optical converters and others photonics applications.

Stationary probability densities of generalized Maxwell-type viscoelastic systems under combined harmonic and Gaussian white noise excitations

Viscoelasticity has been widely studied over the past few decades as a combination of the viscous effects of energy dissipation and the elastic effects of energy storage. As an application, viscoelastic dampers are commonly used to suppress the dynamic behaviour of structures. However, in an actual physical environment, it is difficult to explore the stationary probability densities of random responses for viscoelastic systems. For this purpose, we present a numerical method to investigate the dynamic behaviour of a generalized Maxwell-type viscoelastic system under harmonic and Gaussian white noise excitations. Using approximate equivalent and stochastic averaging, we establish an averaged Ito differential equation for the amplitude of the system. For primary external resonance, we solve the reduced Fokker–Planck–Kolmogorov equation by using the successive over-relaxation technique combined with a finite difference method. Through Monte Carlo simulations, we verify the applicability, accuracy and efficiency of the proposed methodology and demonstrate that viscoelasticity has a significant impact on the dynamic behaviour of the viscoelastic systems. This work reveals the remarkable influences of viscoelasticity, excitation intensities, linear and nonlinear damping and linear and nonlinear stiffness on the probability density functions of system responses, which can guide the selection of materials, stiffnesses and structures in viscoelastic damper design.

Ring Versus Ovoids and Intracavitary Versus Intracavitary-Interstitial Applicators in Cervical Cancer Brachytherapy: Results From the EMBRACE I Study

The aim of this study was to investigate the influence of brachytherapy technique and applicator type on target dose, isodose surface volumes, and organ-at-risk (OAR) dose. Nine hundred two patients treated with tandem/ovoids (T&O) (n = 299) and tandem/ring (T&R) (n= 603) applicators from 16 EMBRACE centers were analyzed. Patients received external beam radiation therapy and magnetic resonance imaging guided brachytherapy with dose prescription according to departmental practice. Centers were divided into 4 groups, according to applicator/technique: Ovoids and ring centers treating mainly with the intracavitary (IC) technique and ovoids and ring centers treating routinely with the intracavitary/interstitial (IC/IS) technique. V85Gy EQD210, CTVHR D90% (EQD210), and bladder, rectum, sigmoid, and vaginal 5-mm lateral-point doses (EQD23) were evaluated among center groups. Differences between T&O and T&R were tested with multivariable analysis. For similar point A doses, mean CTVHR D90% was 3.3 Gy higher and V85Gy was 23% lower for ring-IC compared with ovoids-IC centers (at median target volumes). Mean bladder/rectum doses (D2cm3 and ICRU-point) were 3.2 to 7.7 Gy smaller and vaginal 5-mm lateral-point was 19.6 Gy higher for ring-IC centers. Routine use of IC/IS technique resulted in increased target dose, whereas V85Gy was stable (T&R) or decreased (T&O); reduced bladder and rectum D2cm3 and bladder ICRU-point by 3.5 to 5.0 Gy for ovoids centers; and similar OAR doses for ring centers. CTVHR D90% was 2.8 Gy higher, bladder D2cm3 4.3 Gy lower, rectovaginal ICRU-point 4.8 Gy lower, and vagina 5-mm lateral-point 22.4 Gy higher for ring-IC/IS versus ovoids-IC/IS centers. The P values were <.002 for all comparisons. Equivalently, significant differences were derived from the multivariable analysis. T&R-IC applicators have better target dose and dose conformity than T&O-IC in this representative patient cohort. IC applicators fail to cover large target volumes, whereas routine application of IC/IS improves target and OAR dose considerably. Patients treated with T&R show a more favorable therapeutic ratio when evaluating target, bladder/rectum doses, and V85Gy. A comprehensive view on technique/applicators should furthermore include practical considerations and clinical outcome.

Imaging and Management of Rectal Cancer

High-resolution phased array external magnetic resonance imaging (MRI) is the first investigation of choice in rectal cancer for local staging, both in the primary and restaging situations. Use of MRI helps differentiate between those with good prognosis, which can be offered upfront surgery and the poor prognostic cases where treatment intensification is needed. MRI identified poor prognostic factors are threatened or involved mesorectal fascia, T3 tumors with >5 mm extramural spread, those with extramural vascular invasion, pelvic sidewall nodes and mucinous tumors. At restaging, use of MRI helps evaluate response and an MR tumor regression grading system is being evaluated. Complete response seen on clinical examination and endoscopy, needs confirmation on MRI using both T2-weighted and diffusion-weighted sequences to justify a "watch and wait" approach. In this subset of patients, MRI also plays a role in monitoring and detecting early regrowth. In those with partial response, MRI helps define surgical margins and can be used as a roadmap to decide between sphincter preserving surgeries and radical sphincter sacrificing surgeries; pelvic exenteration and pelvic sidewall lymph node dissection. Poor responders on MRI may benefit from adjuvant chemotherapy. Use of MRI thus helps in individualizing treatment in rectal cancer.

Nonlinear dynamic response of an Euler–Bernoulli beam under a moving mass–spring with large oscillations

This article presents a new approach for the nonlinear dynamic behavior of an Euler–Bernoulli beam under a moving mass. The governing equations for the behavior of the beam under a moving mass in large oscillations including the effect of horizontal and vertical beam displacements are considered via energy method. The systems of governing equations are solved in the condition of external and autoparametric resonance using Galerkin and perturbation methods. In order to validate the solution, the results are compared with a numerical solution and those available in the literature. The governing equations are used for the stability analysis of the beam in different points that will result in spectral responses in stable circumstances.

The anti‐icing and deicing robot system for electricity transmission line based on external excitation resonant

Aiming at the problem of off‐line deicing in overhead transmission lines, such as poor continuity of power supply and possible damage of lines caused by over‐thick deicing, a new online anti‐icing and deicing method based on external excitation resonance is proposed. The theoretical basis of the external excitation resonance to anti‐icing and deicing is established. Then the modal characteristics of the external excitation resonance are determined through the modal analysis of the ice‐coated transmission lines, and the reasonable frequency range of the external excitation resonance is obtained. According to the theoretical analysis and calculation results, the anti‐icing and deicing robot system is designed by the external excitation resonance. Intelligent video technology is used to detect the icing condition of transmission lines in real time, and the vibration frequency range of transmission lines is analyzed and calculated. The vibration frequency is adjusted through the real‐time tracking of the resonance feedback mechanism to ensure the continuity of the resonance working state, so as to effectively realize the efficient anti‐icing and deicing of the transmission lines with the thickness of 1–3 mm at the initial icing stage. Finally, the parameters of the key components of the system are calculated and determined, and the related influencing factors are analyzed. A new deicing theory based on anti‐icing theory is proposed, and specific engineering measures are given. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Exploiting double jumping phenomenon for broadening bandwidth of an energy harvesting device

The steady state response of a particular harvesting system is investigated under the condition of external and internal resonance, with emphasis on the double jump phenomenon. Following the trend of recent researches on exploring nonlinearity aspects for broadening the frequency resonance bandwidth, the problem of effective energy harvesting from a broadband source is dealt with. The proposed harvester can be embedded within vibrational structures and can dually act as a vibration absorber. The governing non-linear partial differential equations are truncated into a set of perturbed equations via Galerkin method. The method of multiple scales is applied to derive the modulated amplitude versus frequency at the vicinity of flapwise and chordwise primary resonances, as well as around other internal resonance frequencies. The amplitude-frequency response plot reveals resonance peaks bending to the left and right, i.e., splitting into two different tongues in contrast to conventional jumps which lean only toward higher or lower frequency directions. Numerical results demonstrate that this internal resonance-based harvesting design can produce sufficient power for the consumption of typical MEMS devices.

Analysis of torsional vibration characteristics and time delay feedback control of semi-direct drive cutting transmission system in shearer

Abstract The semi-direct drive cutting transmission system driven by low speed and high torque permanent magnet synchronous motor (PMSM) in shearer is a typical electromechanical coupling system. In this paper, the torsional vibration characteristics of the transmission system with internal parameter and external cutting load excitation changes are studied. Considering the torsional vibration angle and the air gap magnetic field energy of the PMSM, the torsional vibration model of the electromechanical coupling transmission system is derived by the Lagrange-Maxwell equation. Then, in the case of 1:1 internal resonance and external resonance, the first-order approximate solution is obtained by multiple scale method, and the influence of cutting load excitation and current on the torsional vibration characteristics of the rotor system is analyzed. In addition, the numerical simulation is used to study the vibration jump phenomenon of the nonlinear electromechanical coupling system. The influence of the cutting load excitation on the chaos motion is obtained by the bifurcation diagram and maximum Lyapunov index map. Finally, the vibration amplitude and chaos motion of the rotor system are suppressed by the time delay feedback controller. The research results can provide a theoretical basis for the design and manufacture of the shearer semi-direct drive cutting transmission system.

Stabilizing DFB laser injection-locked to an external fiber-optic ring resonator

Self-injection locking to an external fiber cavity is an efficient technique enabling drastic linewidth narrowing and self-stabilization of semiconductor lasers. The main drawback of this technique is its high sensitivity to fluctuations of the configuration parameters and surroundings. In the proposed laser configuration, to the best our knowledge, for the first time the self-injection locking mechanism is used in conjunction with a simple active optoelectronic feedback, ensuring stable mode-hopping free laser operation in a single longitudinal mode. Locking to 4-m length fiber resonator causes a drastic narrowing of the DFB laser linewidth down to 2.8 kHz and a reduction of the laser phase noise by three orders of magnitude. We have explored key features of the laser dynamics with and without active feedback, revealing stability and tunability of the laser linewidth as an additional benefit of the proposed technique.

Experimental realization of high-efficiency blue light at 426 nm by external frequency doubling resonator

Second harmonic generation (SHG) is used to get continuous wave laser with a lot of applications, it is a major way to provide pump power for generating nonclassical states, especially for squeezed states and entanglement states. High-efficiency SHG resonant on atoms lines also provides laser sources for atomic entanglement generation, light-atom interaction and high-speed quantum memory. For the frequency-doubling process at 426 nm, the major challenge of increasing the conversion efficiency is the thermal effect caused by the absorption in crystal. The degradation of mode-match efficiency induced by the severely thermal effect limits the conversion efficiency of the second harmonic generator. Furthermore, the blue light induced infrared absorption (BLIIRA) in the nonlinear crystal intensifies the thermal effect, it makes the conversion efficiency of the frequency-doubling cavity and the stability of the output blue laser worse, and it is more serious at high input power. Based on the theoretical analysis of thermal lens, we find that the thermal lens should not be placed at the center of the crystal, the location of the equivalently thermals lens has a deviation from the center of the crystal. Follow the theoretical analysis of thermal lens, we design a ring cavity with a 10 mm-long periodically poled potassium titanyle phosphate (PPKTP) crystal to reduce the thermal lens effect induced mode-mismatch. The location of nonlinear crystal is adjusted precisely to reduce the mode-mismatch caused by the thermal lens under our theoretical analysis. Finally, we realized a high conversion efficiency blue laser at 426 nm with the conversion efficiency up to 83.1% with an output power of 428 mW after the adjustment of the crystal location, corresponding to our theoretical analysis well. The measured beam quality factors (&lt;i&gt;M&lt;/i&gt;&lt;sup&gt;2&lt;/sup&gt; value) of the generated blue laser are &lt;inline-formula&gt;&lt;tex-math id="Z-20200217024354-1"&gt;\begin{document}$ M^2(x) = 1.05 $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20191417_Z-20200217024354-1.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20191417_Z-20200217024354-1.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; and &lt;inline-formula&gt;&lt;tex-math id="Z-20200217024354-2"&gt;\begin{document}$ M^2(y) = 1.02 $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20191417_Z-20200217024354-2.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20191417_Z-20200217024354-2.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;, respectively. The measured power stability of Generated Blue laser in 15 mins is 1.25%. The output power of the SHG is strong enough to provide pump power for the generation of the continuous variable squeezed vacuum state at 852 nm and the long-term stability of the output blue laser is also measured to be fine. To the best of our knowledge, the conversion efficiency is the highest-reported one at this wavelength. We believe that such high-performance frequency doubling system is a fundamental building block for quantum information science based non-classical states.

Analysis and Synthesis of Hysteresis Loops in an Oscillator Frequency Characteristic

A methodology for the analysis and synthesis of multiple hysteresis loops in the frequency characteristic of a voltage-controlled oscillator (VCO) is presented. This is achieved through the coupling of an oscillator inductance to multiple external (passive) resonators with resonant frequencies in the tuning range of the VCO. A possible application to the implementation of a compact chipless radio frequency identification (RFID) system is explored, using the oscillator as a reader and placing the external resonators in the tag. The system takes advantage of the high sensitivity to the tag resonances in the presence of hysteresis, which leads to vertical jumps in frequency versus the tuning voltage. A desired bit pattern would be encoded in the tag by enabling or disabling passive resonances at a sequence of frequencies. In the practical realization, the inductors in the oscillator and the external board are implemented through spiral inductors so that the resonators in the VCO and the tag have strong broadside coupling. The coupling effect is modeled through electromagnetic simulations, from which a linear admittance, representing the coupled subnetwork, is extracted. The multihysteresis oscillator characteristic can also be obtained experimentally through a new methodology able to stabilize the physically unstable sections without altering their steady-state values. Different demodulation methods for reading the tag are discussed.

Investigation of the Concentration Dynamics of H2O and HDO Molecules in a Discharge

The results of a joint measurement of the concentration of H2O and HDO molecules in a glow discharge in a quartz tube by the modified method of diode laser spectroscopy with an external resonator are presented. The off-axis radiation input mode makes it possible to determine the parameters of absorption lines at low pressure. The H2O/HDO isotopic ratio in the discharge is measured for different compositions of a plasma-forming mixture. The dynamics of the concentration of water molecules during inlet without discharge is studied and the role of interaction of these molecules with the walls of the facility in the formation of the plasma composition is discussed.

A Filtering Power Divider with Tunable Center Frequency and Wide Stopband

AbstractIn this paper, a tunable power divider (PD) with a good band-pass filtering response using quarter-wavelength stepped impedance resonators (SIRs) is presented. By appropriately adjusting the impedance and electrical length ratio of SIR, the proposed structure can achieve wide stopband performance. Meanwhile, four varactor diodes are loaded to the external resonators to achieve electrical reconfiguration. In addition, a pair of transmission zeros (TZs) can be generated by applying source and load coupling on each side of the passband, which can effectively improve passband selectivity and out-of-band rejection. In order to verify the feasibility of the proposed design method, a prototype circuit of the proposed filtering power divider (FPD) with tunable center frequency is simulated, fabricated and measured. A good agreement between the simulation and measurement results is observed.

ANALYSIS OF FORCED VIBRATIONS OF NONLINEAR PLATES IN A VISCOELASTIC MEDIUM UNDER THE CONDITIONS OF THE DIFFERENT COMBINATIONAL INTERNAL

In the present paper, the force driven dynamic response of a nonlinear plate embedded in a viscoelastic medium, damping features of which are described by the Kelvin-Voigt fractional derivative model, is studied. The motion of the plate is described by three coupled nonlinear differential equations with due account for the fact that the plate is being under the conditions of the internal combinational resonance accompanied by the external resonance, resulting in the interaction of three modes corresponding to the mutually orthogonal displacements. A comparative analysis of numerical calculations for the cases of free and forced vibrations has been carried out.

Force driven vibrations of fractionally damped plates subjected to primary and internal resonances

In the present paper, nonlinear force driven vibrations of thin plates in a viscoelastic medium have been studied, when its damping features are described by the fractional derivative Kelvin-Voigt model. The motion of the plate is governed by a set of three coupled nonlinear differential equations subjected to the different conditions of the internal resonance accompanied by the external resonance, resulting in the interaction of three modes corresponding to the mutually orthogonal displacements. Nonlinear sets of resolving equations in terms of amplitudes and phase differences have been obtained. The influence of fractional order viscosity and external vertical harmonic force on the energy exchange mechanism between the coupled modes has been analyzed.

Chemical Modification of Alginate for Controlled Oral Drug Delivery.

Here, we report two methods that chemically modify alginate to achieve neutral-basic pH sensitivity of the resultant hydrogel. The first method involves direct amide bond formation between alginate and 4-(2-aminoethyl)benzoic acid. The second method that arose out of the desire to achieve better control of the degradation rate of the alginate hydrogel involves reductive amination of oxidized alginate. The products of both methods result in a hydrogel vehicle for targeted delivery of encapsulated payload under physiological conditions in the gastrointestinal tract. Two-dimensional diffusion-ordered spectroscopy and internal and coaxial external nuclear magnetic resonance standards were used to establish chemical bonding and percent incorporation of the modifying groups into the alginate polymer. The hydrogel made with alginate modified by each method was found to be completely stable under acidic pH conditions while disintegrating within minutes to hours in neutral-basic pH conditions. We found that, while alginate oxidation did not affect the β-d-mannuronate/α-l-guluronate ratio of alginate, the rate of disintegration of the hydrogel made with oxidized alginate was dependent upon the degree of oxidation.

Analysis of in-plane 1:1:1 internal resonance of a double cable-stayed shallow arch model with cables’ external excitations

The nonlinear dynamic behaviors of a double cable-stayed shallow arch model are investigated under the one-to-one-to-one internal resonance among the lowest modes of cables and the shallow arch and external primary resonance of cables. The in-plane governing equations of the system are obtained when the harmonic excitation is applied to cables. The excitation mechanism due to the angle-variation of cable tension during motion is newly introduced. Galerkin’s method and the multi-scale method are used to obtain ordinary differential equations (ODEs) of the system and their modulation equations, respectively. Frequency- and force-response curves are used to explore dynamic behaviors of the system when harmonic excitations are symmetrically and asymmetrically applied to cables. More importantly, comparisons of frequency-response curves of the system obtained by two types of trial functions, namely, a common sine function and an exact piecewise function, of the shallow arch in Galerkin’s integration are conducted. The analysis shows that the two results have a slight difference; however, they both have sufficient accuracy to solve the proposed dynamic system.