Science.gov

Sample records for dual mode gadolinium

  1. Dual-mode T1 and T2 magnetic resonance imaging contrast agent based on ultrasmall mixed gadolinium-dysprosium oxide nanoparticles: synthesis, characterization, and in vivo application.

    PubMed

    Tegafaw, Tirusew; Xu, Wenlong; Ahmad, Md Wasi; Baeck, Jong Su; Chang, Yongmin; Bae, Ji Eun; Chae, Kwon Seok; Kim, Tae Jeong; Lee, Gang Ho

    2015-09-11

    A new type of dual-mode T1 and T2 magnetic resonance imaging (MRI) contrast agent based on mixed lanthanide oxide nanoparticles was synthesized. Gd(3+) ((8)S7/2) plays an important role in T1 MRI contrast agents because of its large electron spin magnetic moment resulting from its seven unpaired 4f-electrons, and Dy(3+) ((6)H15/2) has the potential to be used in T2 MRI contrast agents because of its very large total electron magnetic moment: among lanthanide oxide nanoparticles, Dy2O3 nanoparticles have the largest magnetic moments at room temperature. Using these properties of Gd(3+) and Dy(3+) and their oxide nanoparticles, ultrasmall mixed gadolinium-dysprosium oxide (GDO) nanoparticles were synthesized and their potential to act as a dual-mode T1 and T2 MRI contrast agent was investigated in vitro and in vivo. The D-glucuronic acid coated GDO nanoparticles (davg = 1.0 nm) showed large r1 and r2 values (r2/r1 ≈ 6.6) and as a result clear dose-dependent contrast enhancements in R1 and R2 map images. Finally, the dual-mode imaging capability of the nanoparticles was confirmed by obtaining in vivo T1 and T2 MR images. PMID:26291827

  2. Dual-Mode Combustor

    NASA Technical Reports Server (NTRS)

    Trefny, Charles J (Inventor); Dippold, Vance F (Inventor)

    2013-01-01

    A new dual-mode ramjet combustor used for operation over a wide flight Mach number range is described. Subsonic combustion mode is usable to lower flight Mach numbers than current dual-mode scramjets. High speed mode is characterized by supersonic combustion in a free-jet that traverses the subsonic combustion chamber to a variable nozzle throat. Although a variable combustor exit aperture is required, the need for fuel staging to accommodate the combustion process is eliminated. Local heating from shock-boundary-layer interactions on combustor walls is also eliminated.

  3. Dual-Energy X-Radiography With Gadolinium Filter

    NASA Technical Reports Server (NTRS)

    Rutt, Brian

    1987-01-01

    Image resolution increased, and cost reduced. Proposed dual-energy x-ray imaging system, continuous bremsstrahlung spectrum from x-ray tube filtered by foil of nonradioactive gadolinium or another rare-earth metal to form two-peaked energy spectrum. After passing through patient or object under examination, filtered radiation detected by array of energy-discriminating, photon-counting detectors. Detector outputs processed to form x-ray image for each peak and possibly enhanced image based on data taken at both peaks.

  4. Dual-Mode Combustion

    NASA Technical Reports Server (NTRS)

    Goyne, Christopher P.; McDaniel, James C.

    2002-01-01

    The Department of Mechanical and Aerospace Engineering at the University of Virginia has conducted an investigation of the mixing and combustion processes in a hydrogen fueled dual-mode scramjet combustor. The experiment essentially consisted of the "direct connect" continuous operation of a Mach 2 rectangular combustor with a single unswept ramp fuel injector. The stagnation enthalpy of the test flow simulated a flight Mach number of 5. Measurements were obtained using conventional wall instrumentation and laser based diagnostics. These diagnostics included, pressure and wall temperature measurements, Fuel Plume Imaging (FPI) and Particle Image Velocimetry (PIV). A schematic of the combustor configuration and a summary of the measurements obtained are presented. The experimental work at UVa was parallel by Computational Fluid Dynamics (CFD) work at NASA Langley. The numerical and experiment results are compared in this document.

  5. Dual mode nuclear rocket system applications.

    NASA Technical Reports Server (NTRS)

    Boretz, J. E.; Bell, J. M.; Plebuch, R. K.; Priest, C. C.

    1972-01-01

    Mission areas where the dual-mode nuclear rocket system is superior to nondual-mode systems are demonstrated. It is shown that the dual-mode system is competitive with the nondual-mode system even for those specific missions and particular payload configurations where it does not have a clear-cut advantage.

  6. Synergistic enhancement of iron oxide nanoparticle and gadolinium for dual-contrast MRI

    SciTech Connect

    Zhang, Fan; Huang, Xinglu; Qian, Chunqi; Zhu, Lei; Hida, Naoki; Niu, Gang; Chen, Xiaoyuan

    2012-09-07

    Highlights: Black-Right-Pointing-Pointer MR contrast agents exert influence on T{sub 1} or T{sub 2} relaxation time of the surrounding tissue. Black-Right-Pointing-Pointer Combined use of iron oxide and Gd-DTPA can improve the sensitivity/specificity of lesion detection. Black-Right-Pointing-Pointer Dual contrast MRI enhances the delineation of tumor borders and small lesions. Black-Right-Pointing-Pointer The effect of DC-MRI can come from the high paramagnetic susceptibility of Gd{sup 3+}. Black-Right-Pointing-Pointer The effect of DC-MRI can also come from the distinct pharmacokinetic distribution of SPIO and Gd-DTPA. -- Abstract: Purpose: The use of MR contrast agents allows accurate diagnosis by exerting an influence on the longitudinal (T{sub 1}) or transverse (T{sub 2}) relaxation time of the surrounding tissue. In this study, we combined the use of iron oxide (IO) particles and nonspecific extracellular gadolinium chelate (Gd) in order to further improve the sensitivity and specificity of lesion detection. Procedures: With a 7-Tesla scanner, pre-contrasted, IO-enhanced and dual contrast agent enhanced MRIs were performed in phantom, normal animals, and animal models of lymph node tumor metastases and orthotopic brain tumor. For the dual-contrast (DC) MRI, we focused on the evaluation of T{sub 2} weighted DC MRI with IO administered first, then followed by the injection of a bolus of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Results: Based on the C/N ratios and MRI relaxometry, the synergistic effect of coordinated administration of Gd-DTPA and IO was observed and confirmed in phantom, normal liver and tumor models. At 30 min after administration of Feridex, Gd-DTPA further decreased T{sub 2} relaxation in liver immediately after the injection. Additional administration of Gd-DTPA also immediately increased the signal contrast between tumor and brain parenchyma and maximized the C/N ratio to -4.12 {+-} 0.71. Dual contrast MRI also enhanced the

  7. Dual Mode Transmission Designs for Motorcycles

    NASA Astrophysics Data System (ADS)

    Sheu, Kuen-Bao; Yan, Hong-Sen

    This paper presents two types of the dual mode transmission for use in a motorcycle. A motorcycle transmission typically using the discrete speed ratio transmission that works by alternating the gear drive, and the continuously variable transmission (CVT) that transmits power by using the rubber V-belt. The dual mode transmission described in this paper, utilizing a V-belt drive, a fixed ratio mechanism, and a planetary gear train, can provide two operation regimes over the full speed ratio range by means engaged clutches. One is the fixed gear ratio and differential transmission system; the other is the differential and continuously variable transmission system. The kinematics, power flow, and mechanical efficiency of each transmission system are analyzed. An example is employed to illustrate the design procedure. Furthermore, several available design concepts of the dual mode transmissions for motorcycle applications are proposed.

  8. Dual-Mode Adhesive Pad

    NASA Technical Reports Server (NTRS)

    Hartz, Leslie

    1994-01-01

    Tool helps worker grip and move along large, smooth structure with no handgrips or footholds. Adheres to surface but easily released by actuating simple mechanism. Includes handle and segmented contact-adhesive pad. Bulk of pad made of soft plastic foam conforming to surface of structure. Each segment reinforced with rib. In sticking mode, ribs braced by side catches. In peeling mode, side catches retracted, and segmented adhesive pad loses its stiffness. Modified versions useful in inspecting hulls of ships and scaling walls in rescue operations.

  9. Compact Dual-Mode Microwave Antenna

    NASA Technical Reports Server (NTRS)

    Carr, K. L.

    1982-01-01

    Compact dual-mode antenna, 3.66 cm wide by 1.83 cm thick is used both for heating and thermographic detection of tumors in cancer research. Temperature sensor operates independently or simultaneously with heater. Antenna includes 1.6-GHz transmitter and 4.76-GHz receiver. Strip heater between antennas controls temperature of device. Maximum power output is 25 W.

  10. Dual photon absorptiometry using a gadolinium-153 source applied to measure equine bone mineral content

    NASA Astrophysics Data System (ADS)

    Moure, Alessandro; Reichmann, Peter; Remigio Gamba, Humberto

    2003-12-01

    The application of the dual photon absorptiometry (DPA) technique, using gadolinium-153 as the photon source, to evaluate the bone mineral density (BMD) of the third metacarpal bone of horses is presented. The radiation detector was implemented with a NaI(TI) scintillator coupled to a 14 stage photomultiplier. A modular mechanical system allows the position of the prototype to be adjusted in relation to the animal. A moveable carrier makes it possible to scan the third metacarpal with a velocity adjustable between 1 and 12 mm s-1, in steps of 1 mm s-1, for a total distance of 250 mm. The prototype was evaluated with a phantom of the third metacarpal bone made of perspex and aluminium, and in vitro with a transverse slice of the third metacarpal bone of a horse. The tests showed that the prototype has an accuracy and precision of, approximately, 10% and 6%, respectively, for a 6 s acquisition time. Preliminary studies carried out in three foals from birth to one year of age indicated that the prototype is well suited to in vivo and in situ analysis of the BMD of the third metacarpal bones of horses, making it possible to evaluate the changes of BMD levels on a monthly basis. Also, results indicated an exponential behaviour of the BMD curve during the first year of life of the studied horses.

  11. Dual-mode acoustic wave biosensors microarrays

    NASA Astrophysics Data System (ADS)

    Auner, Gregory W.; Shreve, Gina; Ying, Hao; Newaz, Golam; Hughes, Chantelle; Xu, Jianzeng

    2003-04-01

    We have develop highly sensitive and selective acoustic wave biosensor arrays with signal analysis systems to provide a fingerprint for the real-time identification and quantification of a wide array of bacterial pathogens and environmental health hazards. We have developed an unique highly sensitive dual mode acoustic wave platform prototype that, when combined with phage based selective detection elements, form a durable bacteria sensor. Arrays of these new real-time biosensors are integrated to form a biosensor array on a chip. This research and development program optimizes advanced piezoelectric aluminum nitride wide bandgap semiconductors, novel micromachining processes, advanced device structures, selective phage displays development and immobilization techniques, and system integration and signal analysis technology to develop the biosensor arrays. The dual sensor platform can be programmed to sense in a gas, vapor or liquid environment by switching between acoustic wave resonate modes. Such a dual mode sensor has tremendous implications for applications involving monitoring of pathogenic microorganisms in the clinical setting due to their ability to detect airborne pathogens. This provides a number of applications including hospital settings such as intensive care or other in-patient wards for the reduction of nosocomial infections and maintenance of sterile environments in surgical suites. Monitoring for airborn pathogen transmission in public transportation areas such as airplanes may be useful for implementation of strategies for redution of airborn transmission routes. The ability to use the same sensor in the liquid sensing mode is important for tracing the source of airborn pathogens to local liquid sources. Sensing of pathogens in saliva will be useful for sensing oral pathogens and support of decision-making strategies regarding prevention of transmission and support of treatment strategies.

  12. Arterial double-contrast dual-energy MDCT: in-vivo rabbit atherosclerosis with iodinated nanoparticles and gadolinium agents

    NASA Astrophysics Data System (ADS)

    Carmi, Raz; Kafri, Galit; Altman, Ami; Goshen, Liran; Planer, David; Sosna, Jacob

    2010-03-01

    An in-vivo feasibility study of potentially improved atherosclerosis CT imaging is presented. By administration of two different contrast agents to rabbits with induced atherosclerotic plaques we aim at identifying both soft plaque and vessel lumen simultaneously. Initial injection of iodinated nanoparticle (INP) contrast agent (N1177 - Nanoscan Imaging), two to four hours before scan, leads to its later accumulation in macrophage-rich soft plaque, while a second gadolinium contrast agent (Magnevist) injected immediately prior to the scan blends with the aortic blood. The distinction between the two agents in a single scan is achieved with a double-layer dual-energy MDCT (Philips Healthcare) following material separation analysis using the reconstructed images of the different x-ray spectra. A single contrast agent injection scan, where only INP was injected two hours prior to the scan, was compared to a double-contrast scan taken four hours after INP injection and immediately after gadolinium injection. On the single contrast agent scan we observed along the aorta walls, localized iodine accumulation which can point on INP uptake by atherosclerotic plaque. In the double-contrast scan the gadolinium contributes a clearer depiction of the vessel lumen in addition to the lasting INP presence. The material separation shows a good correlation to the pathologies inferred from the conventional CT images of the two different scans while performing only a single scan prevents miss-registration problems and reduces radiation dose. These results suggest that a double-contrast dual-energy CT may be used for advanced clinical diagnostic applications.

  13. Increased wavelength options in the visible and ultraviolet for Raman lasers operating on dual Raman modes.

    PubMed

    Mildren, R P; Piper, J A

    2008-03-01

    We report increased wavelength options from Raman lasers for Raman media having two Raman modes of similar gain coefficient. For an external-cavity potassium gadolinium tungstate Raman laser pumped at 532 nm, we show that two sets of Stokes orders are generated simultaneously by appropriate orientation of the Raman crystal, and also wavelengths that correspond to sums of the two Raman modes. Up to 14 visible Stokes lines were observed in the wavelength range 555-675 nm. The increase in Stokes wavelengths also enables a much greater selection of wavelengths to be accessed via intracavity nonlinear sum frequency and difference frequency mixing. For example, we demonstrate 30 output wavelength options for a wavelength-selectable 271-321 nm Raman laser with intracavity sum frequency mixing in BBO. We also present a theoretical analysis that enables prediction of wavelength options for dual Raman mode systems. PMID:18542414

  14. An Investigation of CTOL Dual-Mode PAVE Concepts

    NASA Technical Reports Server (NTRS)

    Marchman, James F., III; Interatep, Nanyaporn; Skelton, Eugene; Mason, William H.

    2002-01-01

    A study was conducted to assess the feasibility of the dual-mode concept for a personal air vehicle, to determine how constraints differ between the dual-mode concept and a Conventional Takeoff and Landing (CTOL) general aviation aircraft, to recommend a dual-mode vehicle concept, and to recommend areas where further research can contribute to the successful development of a viable PAVE vehicle design.

  15. Costs and energy efficiency of a dual-mode system

    NASA Technical Reports Server (NTRS)

    Heft, R. C.

    1977-01-01

    The life cycle costs of a dual mode system for both public and semiprivate ownership are examined, and the costs in terms of levelized required revenue per passenger mile are presented. The energy use of the dual mode vehicle is analyzed by means of a detailed vehicle simulation program for the control policy and guideway system. Several different propulsion systems are considered.

  16. Dual Mode Inverter Control Test Verification

    SciTech Connect

    Bailey, J.M.

    2001-04-25

    Permanent Magnet Motors with either sinusoidal back emf (permanent magnet synchronous motor [PMSM]) or trapezoidal back emf (brushless dc motor [BDCM]) do not have the ability to alter the air gap flux density (field weakening). Since the back emf increases with speed, the system must be designed to operate with the voltage obtained at its highest speed. Oak Ridge National Laboratory's (ORNL) Power Electronics and Electric Machinery Research Center (PEEMRC) has developed a dual mode inverter controller (DMIC) that overcomes this disadvantage. This report summarizes the results of tests to verify its operation. The standard PEEMRC 75 kW hard-switched inverter was modified to implement the field weakening procedure (silicon controlled rectifier enabled phase advance). A 49.5 hp motor rated at 2800 rpm was derated to a base of 400 rpm and 7.5 hp. The load developed by a Kahn Industries hydraulic dynamometer, was measured with a MCRT9-02TS Himmelstein and Company torque meter. At the base conditions a current of 212 amperes produced the 7.5 hp. Tests were run at 400, 1215, and 2424 rpm. In each run, the current was no greater than 214 amperes. The horsepower obtained in the three runs were 7.5, 9.3, and 8.12. These results verified the basic operation of the DMIC in producing a Constant Power Speed Ratios (CPSR) of six.

  17. Dual mode stereotactic localization method and application

    DOEpatents

    Keppel, Cynthia E.; Barbosa, Fernando Jorge; Majewski, Stanislaw

    2002-01-01

    The invention described herein combines the structural digital X-ray image provided by conventional stereotactic core biopsy instruments with the additional functional metabolic gamma imaging obtained with a dedicated compact gamma imaging mini-camera. Before the procedure, the patient is injected with an appropriate radiopharmaceutical. The radiopharmaceutical uptake distribution within the breast under compression in a conventional examination table expressed by the intensity of gamma emissions is obtained for comparison (co-registration) with the digital mammography (X-ray) image. This dual modality mode of operation greatly increases the functionality of existing stereotactic biopsy devices by yielding a much smaller number of false positives than would be produced using X-ray images alone. The ability to obtain both the X-ray mammographic image and the nuclear-based medicine gamma image using a single device is made possible largely through the use of a novel, small and movable gamma imaging camera that permits its incorporation into the same table or system as that currently utilized to obtain X-ray based mammographic images for localization of lesions.

  18. Passively Q-switched and mode-locked dual-wavelength Nd:GGG laser with Cr4+:YAG as a saturable absorber

    NASA Astrophysics Data System (ADS)

    Chu, Hongwei; Zhao, Shengzhi; Li, Yufei; Yang, Kejian; Li, Guiqiu; Li, Dechun; Zhao, Jia; Qiao, Wenchao; Li, Tao; Feng, Chuansheng; Zhang, Haijuan

    2014-03-01

    By using neodymium-doped gadolinium gallium garnet (Nd:GGG) as a laser medium, a simultaneously passively Q-switched and mode-locked (QML) dual-wavelength laser with Cr4+:YAG as a saturable absorber is presented. The laser simultaneously oscillated at 1061 nm and 1063 nm, corresponding to a frequency difference of 0.53 THz. QML pulses with nearly 100% modulation depth were observed. The mode-locked pulse duration underneath the Q-switched envelope was estimated to be about 908 ps. The experimental results indicated that the dual-wavelength QML Nd:GGG laser can be an excellent candidate for the generation of THz waves.

  19. Slant-hole collimator, dual mode sterotactic localization method

    DOEpatents

    Weisenberger, Andrew G.

    2002-01-01

    The use of a slant-hole collimator in the gamma camera of dual mode stereotactic localization apparatus allows the acquisition of a stereo pair of scintimammographic images without repositioning of the gamma camera between image acquisitions.

  20. Dual-Mode Scramjet Flameholding Operability Measurements

    NASA Technical Reports Server (NTRS)

    Donohue, James M.

    2012-01-01

    Flameholding measurements were made in two different direct connect combustor facilities that were designed to simulate a cavity flameholder in the flowfield of a hydrocarbon fueled dual-mode scramjet combustor. The presence of a shocktrain upstream of the flameholder has a significant impact on the inlet flow to the combustor and on the flameholding limits. A throttle was installed in the downstream end of the test rigs to provide the needed back-pressurization and decouple the operation of the flameholder from the backpressure formed by heat release and thermal choking, as in a flight engine. Measurements were made primarily with ethylene fuel but a limited number of tests were also performed with heated gaseous JP-7 fuel injection. The flameholding limits were measured by ramping inlet air temperature down until blowout was observed. The tests performed in the United Technologies Research Center (UTRC) facility used a hydrogen fueled vitiated air heater, Mach 2.2 and 3.3 inlet nozzles, a scramjet combustor rig with a 1.666 by 6 inch inlet and a 0.65 inch deep cavity. Mean blowout temperature measured at the baseline condition with ethylene fuel, the Mach 2.2 inlet and a cavity pressure of 21 psia was 1502 oR. Flameholding sensitivity to a variety of parameters was assessed. Blowout temperature was found to be most sensitive to fuel injection location and fuel flowrates and surprisingly insensitive to operating pressure (by varying both back-pressurization and inlet flowrate) and inlet Mach number. Video imaging through both the bottom and side wall windows was collected simultaneously and showed that the flame structure was quite unsteady with significant lateral movements as well as movement upstream of the flameholder. Experiments in the University of Virginia (UVa) test facility used a Mach 2 inlet nozzle with a 1 inch by 1.5 inch exit cross section, an aspect ratio of 1.5 versus 3.6 in the UTRC facility. The UVa facility tests were designed to measure the

  1. Financial Management of Distance Learning in Dual-Mode Institutions

    ERIC Educational Resources Information Center

    Rumble, Greville

    2012-01-01

    Dual-mode universities operating in a tough economic environment need to be able to answer a range of questions concerning their use of different teaching modes accurately and with confidence. Only an activity-based costing approach will provide them with this tool. Cost studies of other distance learning projects may provide benchmarks against…

  2. Simultaneous Dual-Wavelength Operation of Nd-Doped Yttrium Orthovanadate Self-Raman Laser at 1175 nm and Undoped Gadolinium Orthovanadate Raman Laser at 1174 nm

    NASA Astrophysics Data System (ADS)

    Shen, Hongbin; Wang, Qingpu; Zhang, Xingyu; Zhang, Lei; Zhang, Chu; Chen, Xiaohan; Cong, Zhenhua; Bai, Fen; Liu, Zhaojun

    2013-04-01

    A diode-pumped actively Q-switched Nd-doped yttrium orthovanadate self-Raman emission at 1175 nm and undoped gadolinium orthovanadate Raman emission at 1174 nm dual-wavelength laser is demonstrated. With the pump power of 20.5 W and pulse repetition frequency of 20 kHz, the maximum dual-wavelength output power of 1.52 W was obtained, which contained a 0.71 W 1174 nm Raman laser component and a 0.81 W 1175 nm self-Raman laser component. The corresponding dual-wavelength Raman pulse width was 14.8 ns. Experimental results indicated that the dual-wavelength Raman laser with a small wavelength separation was effectively realized through simultaneous self-Raman and Raman shift.

  3. Dual Mode Shock-Expansion/Reflected-Shock Tunnel

    NASA Technical Reports Server (NTRS)

    Erdos, John I.; Bakos, Robert J.; Castrogiovanni, Anthony; Rogers, R. Clayton

    1998-01-01

    NASA s HYPULSE facility at GASL has been reconfigured to permit free jet testing of the Hyper-X flowpath at flight Mach numbers of 7 and 10. Among the required changes are addition of a converging-diverging nozzle to permit operation in a reflected shock tunnel mode, a 7 ft. diameter test cabin and a 30 in. diameter contoured nozzle. However, none of these changes were allowed to interfere with rapid recovery of the prior shock-expansion tunnel mode of operation, and indeed certain changes should enhance facility usefulness and productivity in either mode. A previously-developed shock-induced detonation mode of driving the facility has been successfully applied to both reflected shock tunnel operation at Mach 10 flight conditions, with tailored interface operation, and shock-expansion tunnel operation at flight conditions corresponding to Mach numbers from 12 to 25. Tailored interface operation at Mach 7 has been achieved with an unheated helium driver. In the present paper, the rationale for a dual mode shock expansion/reflected shock tunnel is discussed, and the capabilities and limitations for each mode are outlined. The physical changes in the HYPULSE facility to achieve dual mode capability are also described. Limited calibration data obtained to date in the new reflected shock tunnel mode are presented and the anticipated flight simulation map with dual mode operation is also outlined.

  4. Dual-mode temperature compensation technique for laser stabilization to a crystalline whispering gallery mode resonator.

    PubMed

    Fescenko, I; Alnis, J; Schliesser, A; Wang, C Y; Kippenberg, T J; Hänsch, T W

    2012-08-13

    Frequency stabilization of a diode laser locked to a whispering gallery mode (WGM) reference resonator made of a MgF2 single crystal is demonstrated. The strong thermal dependence of the difference frequency between two orthogonally polarized TE an TM modes (dual-mode frequency) of the optically anisotropic crystal material allows sensitive measurement of the resonator's temperature within the optical mode volume. This dual-mode signal was used as feedback for self-referenced temperature stabilization to nanokelvin precision, resulting in frequency stability of 0.3 MHz/h at 972 nm, which was measured by comparing with an independent ultrastable laser. PMID:23038559

  5. Dual-Band Dual-Mode Substrate Integrated Waveguide Filters with Independently Reconfigurable TE101 Resonant Mode

    PubMed Central

    Wu, Yongle; Chen, Yuqing; Jiao, Lingxiao; Liu, Yuanan; Ghassemlooy, Zabih

    2016-01-01

    A novel perturbation approach using additional metalized via-holes for implementation of the dual-band or wide-band dual-mode substrate integrated waveguide (SIW) filters is proposed in this paper. The independent perturbation on the first resonant mode TE101 can be constructed by applying the proposed perturbation approach, whereas the second resonant mode TE102 is not affected. Thus, new kinds of dual-band or wide-band dual-mode SIW filters with a fixed or an independently reconfigurable low-frequency band have been directly achieved. In order to experimentally verify the proposed design method, four two-cavity dual-band SIW filters, which have different numbers of perturbation via-holes in each cavity, and a two-cavity dual-band SIW filter, which includes four via-holes and eight reconfigurable states in each cavity, are designed and experimentally assessed. The measured results indicate that the available frequency-ratio range from 1 to 1.3 can be realized by using four two-cavity dual-band SIW filters. The center frequency of the first band can be tuned from 4.61 GHz to 5.24 GHz, whereas the center frequency of the second one is fixed at around 6.18 GHz for the two-cavity dual-band SIW filter with four reconfigurable states via-holes. All the simulated and measured results show an acceptable agreement with the predicted data. PMID:27561687

  6. Dual-Band Dual-Mode Substrate Integrated Waveguide Filters with Independently Reconfigurable TE101 Resonant Mode.

    PubMed

    Wu, Yongle; Chen, Yuqing; Jiao, Lingxiao; Liu, Yuanan; Ghassemlooy, Zabih

    2016-01-01

    A novel perturbation approach using additional metalized via-holes for implementation of the dual-band or wide-band dual-mode substrate integrated waveguide (SIW) filters is proposed in this paper. The independent perturbation on the first resonant mode TE101 can be constructed by applying the proposed perturbation approach, whereas the second resonant mode TE102 is not affected. Thus, new kinds of dual-band or wide-band dual-mode SIW filters with a fixed or an independently reconfigurable low-frequency band have been directly achieved. In order to experimentally verify the proposed design method, four two-cavity dual-band SIW filters, which have different numbers of perturbation via-holes in each cavity, and a two-cavity dual-band SIW filter, which includes four via-holes and eight reconfigurable states in each cavity, are designed and experimentally assessed. The measured results indicate that the available frequency-ratio range from 1 to 1.3 can be realized by using four two-cavity dual-band SIW filters. The center frequency of the first band can be tuned from 4.61 GHz to 5.24 GHz, whereas the center frequency of the second one is fixed at around 6.18 GHz for the two-cavity dual-band SIW filter with four reconfigurable states via-holes. All the simulated and measured results show an acceptable agreement with the predicted data. PMID:27561687

  7. Two-dimension lateral shearing interferometry with dual-mode

    NASA Astrophysics Data System (ADS)

    Liu, Zhixiang; Xin, Tingwen; Jiang, Yadong; Lv, Baobin; Xu, Fuchao

    2015-09-01

    Lateral shearing interferometry is an attractive technique to measure the wavefront aberration of high numerical aperture optical systems, of which using two-dimensional grating can divide and shear the wavefront in two-dimension simultaneously. A two-dimension lateral shearing interferometer based on chessboard grating was designed, which can work in dual-mode: the phase shifting mode and the Fourier transform mode. In the phase shifting mode, the phase shifting was realized by moving chessboard grating along the shearing direction in the image plane. In the Fourier transform mode, the spatial carrier frequency was realized by positioning the grating at the Talbot distance of the objective image plane. An experimental setup was designed to measure a 10×, NA0.25 microscope objective at 632.8nm wavelength. The objective was measured by the experimental setup in dual-mode, the results showed that the wavefront of the objective was 0.172λ RMS; in the phase shifting mode, the repeatability (3σ) of RMS was 1.1mλ in the Fourier transform mode, the repeatability (3σ) of RMS was 2.7mλ after correcting the coordinates of the wavefront, the differences of Z5 to Z36 between phase shifting mode and the Fourier transform mode were better than 8mλ.

  8. Dual-cavity mode converter for a fundamental mode output in an over-moded relativistic backward-wave oscillator

    SciTech Connect

    Li, Jiawei; Huang, Wenhua; Xiao, Renzhen; Bai, Xianchen; Zhang, Yuchuan; Zhang, Xiaowei; Shao, Hao; Chen, Changhua; Zhu, Qi

    2015-03-16

    A dual-cavity TM{sub 02}–TM{sub 01} mode converter is designed for a dual-mode operation over-moded relativistic backward-wave oscillator. With the converter, the fundamental mode output is achieved. Particle-in-cell simulation shows that the efficiency of beam-wave conversion was over 46% and a pureTM{sub 01} mode output was obtained. Effects of end reflection provided by the mode converter were studied. Adequate TM{sub 01} mode feedback provided by the converter enhances conversion efficiency. The distance between the mode converter and extraction cavity critically affect the generation of microwaves depending on the reflection phase of TM{sub 01} mode feedback.

  9. Dual mode acoustic wave sensor for precise pressure reading

    NASA Astrophysics Data System (ADS)

    Mu, Xiaojing; Kropelnicki, Piotr; Wang, Yong; Randles, Andrew Benson; Chuan Chai, Kevin Tshun; Cai, Hong; Gu, Yuan Dong

    2014-09-01

    In this letter, a Microelectromechanical system acoustic wave sensor, which has a dual mode (lateral field exited Lamb wave mode and surface acoustic wave (SAW) mode) behavior, is presented for precious pressure change read out. Comb-like interdigital structured electrodes on top of piezoelectric material aluminium nitride (AlN) are used to generate the wave modes. The sensor membrane consists of single crystalline silicon formed by backside-etching of the bulk material of a silicon on insulator wafer having variable device thickness layer (5 μm-50 μm). With this principle, a pressure sensor has been fabricated and mounted on a pressure test package with pressure applied to the backside of the membrane within a range of 0 psi to 300 psi. The temperature coefficient of frequency was experimentally measured in the temperature range of -50 °C to 300 °C. This idea demonstrates a piezoelectric based sensor having two modes SAW/Lamb wave for direct physical parameter—pressure readout and temperature cancellation which can operate in harsh environment such as oil and gas exploration, automobile and aeronautic applications using the dual mode behavior of the sensor and differential readout at the same time.

  10. Numerical Simulation of Dual-Mode Scramjet Combustors

    NASA Technical Reports Server (NTRS)

    Rodriguez, C. G.; Riggins, D. W.; Bittner, R. D.

    2000-01-01

    Results of a numerical investigation of a three-dimensional dual-mode scramjet isolator-combustor flow-field are presented. Specifically, the effect of wall cooling on upstream interaction and flow-structure is examined for a case assuming jet-to-jet symmetry within the combustor. Comparisons are made with available experimental wall pressures. The full half-duct for the isolator-combustor is then modeled in order to study the influence of side-walls. Large scale three-dimensionality is observed in the flow with massive separation forward on the side-walls of the duct. A brief review of convergence-acceleration techniques useful in dual-mode simulations is presented, followed by recommendations regarding the development of a reliable and unambiguous experimental data base for guiding CFD code assessments in this area.

  11. Stable multiwavelength single longitudinal mode dual ring Brillouin fiber laser

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Yu, Jin-Long; Wang, Wen-Rui; Pan, Hong-Gang; Yang, En-Ze

    2015-04-01

    A novel stable multiwavelength single longitudinal mode (SLM) dual ring Brillouin fiber laser is proposed and demonstrated. Dual ring configuration with 100 and 10 m length of single mode fiber guarantees each Stokes and anti-Stokes waves in SLM status. Linewidth of the first Stokes wave is below 4 kHz with 60 dB sidemode suppression value. 7 stable SLM lasing wavelengths including the pump with a 5 dB bandwidth of 0.5, 0.084 nm wavelength spacing and 15 dB average optical signal-to-noise ratio are generated through the cascaded SBS and degenerate FWM process. The laser can freely be tuned 30 nm range from 1535 to 1565 nm. The power fluctuation of the first Stokes wave is about 8 % measured by Data Acquisition System in 1 h.

  12. Development and Use of the Dual-Mode Plasma Torch

    SciTech Connect

    Womack, R.; Shuey, M.

    2002-02-26

    After several years of development, a commercially available high-temperature treatment system has been developed and installed that treats heterogeneous low-level radioactive waste. High temperature plasma processing, unique torch design and operating features make it feasible to achieve a volume reduced, permanent, high integrity waste form while eliminating the personnel exposure and costs associated with conventional sorting, characterizing and handling. Plasma technology can also be used to treat previous conditioned waste packages that no longer meet the current acceptance criteria for final disposal. Plasma treatment can result, in many cases, in a substantial volume reduction, which lowers the final disposal costs. This paper covers the recently patented dual mode plasma torch design(1), the lessons learned that fostered its development and the advantages it brings to radioactive waste processing. This paper also provides current full scale Plasma Arc Centrifugal Treatment (PACT) project status and how the dual mode torch is being used in the PACT system.

  13. Testing a dual-mode ramjet engine with kerosene combustion

    NASA Astrophysics Data System (ADS)

    Levin, V. M.; Karasev, V. N.; Kartovitskii, L. L.; Krymov, E. A.; Skachkov, O. A.

    2015-09-01

    Results of life firing tests of a dual-mode ramjet engine intended for operation in the speed range M = 3-6 are discussed. The tests were carried out on a test bench under freestream conditions typical of Mach 6 flight at 27.6-km altitude. In the tests, the adopted design and technological solutions were verified, and efficient operation of the ramjet engine with kerosene combustion during 110 s was demonstrated.

  14. Strict dual-mode large-mode-area fiber with multicore structure

    NASA Astrophysics Data System (ADS)

    Jin, Wenxing; Ren, Guobin; Jian, Wei; Jiang, Youchao; Wu, Yue; Yang, Yuguang; Shen, Ya; Jian, Shuisheng

    2016-05-01

    In this paper, we proposed a new kind of quasi-37-cores fiber structure consisting of 15 conventional cores and 22 air-hole cores. Strict dual-mode condition is systematically analyzed about three structure parameters, core-to-core pitch, relative core diameter, and difference of refractive index between core and cladding. Large effective area about 1910.98 μm2 with low bending loss less than 10-3 dB / m is achieved while keeping strict dual-mode. This structured fiber has a great potential in high power fiber lasers and amplifiers.

  15. Analysis of mode switching algorithms in dual chamber pacemakers.

    PubMed

    Israel, Carsten W

    2002-03-01

    Dual chamber systems are currently implanted in an increasing number of patients with a pacing indication and paroxysmal atrial tachyarrhythmias (ATAs). To avoid tracking of high atrial rates during ATA while providing AV synchronous pacing during sinus rhythm and AV block, automatic mode switching (MS) to a nontracking mode has been developed. Several concepts of MS algorithms have been introduced differing in sensitivity and specificity of ATA detection, delay between ATA onset and MS, pacing mode during MS, rapidity of MS termination upon detection of sinus rhythm, and special algorithms pertinent to MS. This review classifies and analyzes algorithms that are integrated into MS concepts and outlines considerations on optimal MS performance. Based on simulations and clinical studies, fast MS concepts avoiding high paced ventricular rates seem preferable but require special functions to avoid loss of AV synchrony by inappropriate MS. Similarly, fast return to tracking mode after ATA cessation seems preferable but requires algorithms to prevent mode oscillations. Sudden ventricular rate changes have to be avoided by rate smoothing functions, and an appropriate ventricular rate during nontracking mode has to be provided by rate responsive pacing. Programming of the device includes individual optimization of atrial sensitivity, atrial blanking times, and tachycardia detection rates. In addition, a high signal-to-noise ratio by careful atrial lead implantation, narrowly spaced bipolar atrial leads and a good sensing amplifier, together with special algorithms for atrial sensing adjustment improve the performance of MS algorithms. PMID:11990674

  16. Dual mode use requirements analysis for the institutional cluster.

    SciTech Connect

    Leland, Robert W.

    2003-09-01

    This paper analyzes what additional costs would be incurred in supporting dual-mode, i.e. both classified and unclassified use of the Institutional Computing (IC) hardware. The following five options are considered: periods processing in which a fraction of the system alternates in time between classified and unclassified modes, static split in which the system is constructed as a set of smaller clusters which remain in one mode or the other, re-configurable split in which the system is constructed in a split fashion but a mechanism is provided to reconfigure it very infrequently, red/black switching in which a mechanism is provided to switch sections of the system between modes frequently, and complementary operation in which parts of the system are operated entirely in one mode at one geographical site and entirely in the other mode at the other geographical site and other systems are repartitioned to balance work load. These options are evaluated against eleven criteria such as disk storage costs, distance computing costs, reductions in capability and capacity as a result of various factors etc. The evaluation is both qualitative and quantitative, and is captured in various summary tables.

  17. Dual-polarization and dual-mode orbital angular momentum radio vortex beam generated by using reflective metasurface

    NASA Astrophysics Data System (ADS)

    Yu, Shixing; Li, Long; Shi, Guangming

    2016-08-01

    A metasurface, which is composed of printed cross-dipole elements with different arm lengths, is designed, fabricated, and experimentally demonstrated to generate orbital angular momentum (OAM) vortex waves of dual polarizations and dual modes in the radio frequency domain simultaneously. The prototype of a practical metasurface is fabricated and measured to validate the results of theoretical analysis and design at 5.8 GHz. Numerical and experimental results verify that vortex waves with dual OAM modes and dual polarizations can be flexibly generated by using a reflective metasurface. The proposed method paves a way to generate diverse OAM vortex waves for radio frequency and microwave wireless communication applications.

  18. In vitro testing of dual-mode thulium microsurgical laser

    NASA Astrophysics Data System (ADS)

    Keller, Matthew D.; Stafford, James A.; Schmidt, Brandon P.; Wells, Jonathon D.

    2012-02-01

    Recently, thulium (Tm) fiber lasers have been investigated for use in surgical procedures, especially in urology, because of their numerous advantages over existing laser systems. Lockheed Martin Aculight has recently developed the first truly dual-mode Tm laser, which can be operated in either CW or in short-pulsed mode to produce high peak power. The goal of this study was to assess both the soft tissue ablation performance of this laser in vitro and the feasibility of using it for lithotripsy. Ablation tests were performed on liver tissue, chicken breast, and porcine skin, using a 100μm or 200μm delivery fiber, and operated in CW mode or pulsed (~350ns pulse widths) at 10kHz or 1kHz. Ablation efficiencies for long (3 minutes) exposures and collateral damage zones for short (3-5 seconds) exposures were determined for the different pulse modes and a range of pulse energies. In all tissues, the most energy-efficient ablation occurred for the 10kHz pulsed mode operating just above ablation threshold, while the highest mass removal rate occurred in 10kHz pulsed mode operating at max energy (2.1 mJ). In histological sections from short exposures, 10kHz pulsed exposures created slightly smaller thermal coagulation zones than energy-matched CW exposures, while 1kHz deliveries had substantially smaller thermal damage zones. In addition, using a 100μm fiber, the 10kHz mode was able to fragment samples of uric acid stones.

  19. Focusing-schlieren visualization in a dual-mode scramjet

    NASA Astrophysics Data System (ADS)

    Kouchi, Toshinori; Goyne, Christopher P.; Rockwell, Robert D.; McDaniel, James C.

    2015-12-01

    Schlieren imaging is particularly suited to measuring density gradients in compressible flowfields and can be used to capture shock waves and expansion fans, as well as the turbulent structures of mixing and wake flows. Conventional schlieren imaging, however, has difficulty clearly capturing such structures in long-duration supersonic combustion test facilities. This is because the severe flow temperatures locally change the refractive index of the window glass that is being used to provide optical access. On the other hand, focusing-schlieren imaging presents the potential of reduced sensitivity to thermal distortion of the windows and to clearly capture the flow structures even during a combustion test. This reduced sensitivity is due the technique's ability to achieve a narrow depth of focus. As part of this study, a focusing-schlieren system was developed with a depth of focus near ±5 mm and was applied to a direct-connect, continuous-flow type, supersonic combustion test facility with a stagnation temperature near 1200 K. The present system was used to successfully visualize the flowfield inside a dual-mode scramjet. The imaging system captured combustion-induced volumetric expansion of the fuel jet and an anchored bifurcated shock wave at the trailing edge of the ramp fuel injector. This is the first time successful focusing-schlieren measurements have been reported for a dual-mode scramjet.

  20. Dual-Pump CARS Measurements in the University of Virginia's Dual-Mode Scramjet: Configuration "C"

    NASA Technical Reports Server (NTRS)

    Cutler, Andrew D.; Magnotti, Gaetano; Cantu, Luca; Gallo, Emanuela; Danehy, Paul M.; Rockwell, Robert; Goyne, Christopher; McDaniel, James

    2013-01-01

    Measurements have been conducted at the University of Virginia Supersonic Combustion Facility in configuration C of the dual-mode scramjet. This is a continuation of previously published works on configuration A. The scramjet is hydrogen fueled and operated at two equivalence ratios, one representative of the scram mode and the other of the ram mode. Dual-pump CARS was used to acquire the mole fractions of the major species as well as the rotational and vibrational temperatures of N2. Developments in methods and uncertainties in fitting CARS spectra for vibrational temperature are discussed. Mean quantities and the standard deviation of the turbulent fluctuations at multiple planes in the flow path are presented. In the scram case the combustion of fuel is completed before the end of the measurement domain, while for the ram case the measurement domain extends into the region where the flow is accelerating and combustion is almost completed. Higher vibrational than rotational temperature is observed in those parts of the hot combustion plume where there is substantial H2 (and hence chemical reaction) present.

  1. In Vivo Tracking of Phagocytic Immune Cells Using a Dual Imaging Probe with Gadolinium-Enhanced MRI and Near-Infrared Fluorescence.

    PubMed

    Kim, Eun-Joong; Bhuniya, Sankarprasad; Lee, Hyunseung; Kim, Hyun Min; Shin, Weon Sup; Kim, Jong Seung; Hong, Kwan Soo

    2016-04-27

    A novel dual imaging probe for in vivo magnetic resonance imaging (MRI) and optical imaging was developed by combining gadolinium (Gd)-chelating MR probe and a near-infrared (NIR) fluorophore, aza-BODIPY (AB; BODIPY = boron-dipyrromethene). This aza-BODIPY-based bimodal contrast agent (AB-BCA) showed a significant fluorescence emission around the NIR range and an enhanced longitudinal relaxivity in MR modality. The probe was easily delivered to phagocytic cells of the innate immune system, together with macrophages and dendritic cells (DCs), and presented high-performance fluorescence and MR imaging without obvious cytotoxicity. For in vivo visualization of AB-BCA using MRI and optical imaging, bone marrow-derived DCs were labeled and injected into the footpad of mice, and labeled DCs were tracked in vivo. We observed the migration of AB-BCA-labeled DCs into the lymph nodes via lymphatic vessels using NIR fluorescence and T1-weighted MR images. This dual-modality imaging probe was used for noninvasive monitoring of DC migration into lymph nodes and could be useful for investigating advanced cellular immunotherapy. PMID:27058603

  2. The convertible engine: A dual-mode propulsion system

    NASA Technical Reports Server (NTRS)

    Mcardle, Jack G.

    1988-01-01

    A variable inlet guide vane (VIGV) convertible engine that could be used to power future high-speed rotorcraft was tested on an outdoor stand. The engine ran stably and smoothly in the turbofan, turboshaft, and dual (combined fan and shaft) power modes. In the turbofan mode with the VIGV open, fuel consumption was comparable to that of a conventional turbofan engine. In the turboshaft mode with the VIGV closed, fuel consumption was higher than that of present turboshaft engines because power was wasted in churning fan-tip air flow. In dynamic performance tests with a specially built digital engine control and using a waterbrake dynamometer for shaft load, the engine responded effectively to large steps in thrust command and shaft torque. Previous mission analyses of a conceptual X-wing rotorcraft capable of 400-knot cruise speed were revised to account for more fan-tip churning power loss that was originally estimated. The calculations confirm that using convertible engines rather than separate life and cruise engines would result in a smaller, lighter craft with lower fuel use and direct operating cost.

  3. Dual mode-locked swept sources for SS-OCT

    NASA Astrophysics Data System (ADS)

    Stancu, Radu F.; Podoleanu, Adrian G.

    2016-03-01

    A novel dual-mode-locking mechanism was developed in order to tune an akinetic swept source (AKSS) based on dispersive cavity at a repetition rate close to, but slightly different from the inverse of the cavity roundtrip. Several optical source configurations emitting in the 1060 nm or 1550 nm wavelength region were developed, characterized and tested in OCT applications. For the 1550 nm swept source employing a Faraday rotating mirror in a dispersive cavity, sweeping rates in the range of MHz were achieved, from 782 kHz to up to 5 times this value, with proportional decrease in the tuning bandwidth. Linewidths smaller than 60 pm and output powers exceeding a few mW were measured. The 1060 nm swept source implemented was used to generate OCT images of a pressure sensitive adhesive.

  4. Probing dual mode emission of Eu3+ in garnet phosphor

    NASA Astrophysics Data System (ADS)

    Singh, S. K.; Gi Lee, Dong; Soo Yi, Soung; Jang, Kiwan; Shin, Dong-Soo; Hyun Jeong, Jung

    2013-05-01

    Eu3+ doped and Eu3+, Yb3+ co-doped Gd3Ga5O12 phosphors have been developed by facile solid state reaction method which can be easily scaled-up in large quantity. The synthesis has been optimized to get a single phase material at 1300 °C. The phase and crystal parameters have been analyzed by using X-ray diffraction measurement. Photoluminescence excitation (monitored for the 5D0 → 7F1 transition of Eu3+) depicts that the active ion (Eu3+) can be excited through direct excitation into 4f band of Eu3+, through charge transfer band (Eu3+-O2-) excitation and also through the excitation into 8S7/2 → 6IJ intra f-f transition of Gd3+ ion, which significantly all together cover a broad excitation region in 200-420 nm. In addition, in the presence of Yb3+ ions, the emission is also achieved by near infrared excitation (976 nm), through a typical upconversion (UC) process. Thus, the material efficiently behaves as a dual mode emitting phosphor (emission is achieved both through normal fluorescence and through UC process). The conversion efficiency of silicon solar cells is only 15% of terrestrial solar energy for 200-400 nm region and also the sub-band gap energy (in infrared region) is lost as heat; therefore, this kind of dual mode phosphors may be used to overcome the above mentioned incomplete utilization of the solar spectrum and can open realm of new possibilities for energy harvesting.

  5. Dual-Mode Universities in Higher Education: Way Station or Final Destination?

    ERIC Educational Resources Information Center

    Daniel, John

    2012-01-01

    In the title the author asked whether dual-mode institutions were a stable "final" model for higher education or a step on the way to something else. Only a few institutions seem able to function in dual mode (i.e. with distinct groups of distance and classroom students) in a successful and sustainable way. Some institutions now claim that all…

  6. A dual-mode thickness-shear quartz pressure sensor.

    PubMed

    Besson, R J; Boy, J J; Glotin, B; Jinzaki, Y; Sinha, B; Valdois, M

    1993-01-01

    The development of a dual-mode thickness-shear quartz pressure sensor to meet the demanding performance requirements of oil-field applications is discussed. The objective was to develop a sensor with an operating pressure range of 0-103.42 MPa (0.15 000 lb/in(2)), a temperature range of -10 to +175 degrees C, a pressure calibration accuracy of 6894.8 Pa (1 lb/in(2)), and resolution of 68.95 Pa (0.01 lb/in(2)) with 1-s counter gate time. Doubly rotated cuts with piezoelectric coupling to both the C-modes of vibration were investigated. A theoretical study and general design considerations in the development of such sensors are described. Experimental results were obtained for two sensor designs: one uses a cylindrical design with the SBTC-cut, and the other, called SPA, is a special resonator design vibrating around 5 MHz without any activity dips. Pressure sensitivity of approximately 145 Hz/MPa (1 Hz/lb/in(2)) at 175 degrees C is obtained. Laboratory evaluation of the static and dynamic performances is discussed for the prototypes based on the SPA design. PMID:18263223

  7. Testing and analysis of dual-mode adaptive landing gear, taxi mode test system for YF-12A

    NASA Technical Reports Server (NTRS)

    Gamon, M. A.

    1979-01-01

    The effectiveness of a dual mode adaptive landing gear system in reducing the dynamic response of an airplane during ground taxiing was studied. The dynamic taxi tests of the YF-12A research airplane are presented. A digital computer program which simulated the test conditions is discussed. The dual mode system as tested provides dynamic taxi response reductions of 25 percent at the cg and 30 to 45 percent at the cockpit.

  8. HIFU Monitoring and Control with Dual-Mode Ultrasound Arrays

    NASA Astrophysics Data System (ADS)

    Casper, Andrew Jacob

    The biological effects of high-intensity focused ultrasound (HIFU) have been known and studied for decades. HIFU has been shown capable of treating a wide variety of diseases and disorders. However, despite its demonstrated potential, HIFU has been slow to gain clinical acceptance. This is due, in part, to the difficulty associated with robustly monitoring and controlling the delivery of the HIFU energy. The non-invasive nature of the surgery makes the assessment of treatment progression difficult, leading to long treatment times and a significant risk of under treatment. This thesis research develops new techniques and systems for robustly monitoring HIFU therapies for the safe and efficacious delivery of the intended treatment. Systems and algorithms were developed for the two most common modes of HIFU delivery systems: single-element and phased array applicators. Delivering HIFU with a single element transducer is a widely used technique in HIFU therapies. The simplicity of a single element offers many benefits in terms of cost and overall system complexity. Typical monitoring schemes rely on an external device (e.g. diagnostic ultrasound or MRI) to assess the progression of therapy. The research presented in this thesis explores using the same element to both deliver and monitor the HIFU therapy. The use of a dual-mode ultrasound transducer (DMUT) required the development of an FPGA based single-channel arbitrary waveform generator and high-speed data acquisition unit. Data collected from initial uncontrolled ablations led to the development of monitoring and control algorithms which were implemented directly on the FPGA. Close integration between the data acquisition and arbitrary waveform units allowed for fast, low latency control over the ablation process. Results are presented that demonstrate control of HIFU therapies over a broad range of intensities and in multiple in vitro tissues. The second area of investigation expands the DMUT research to an

  9. One-pot aqueous synthesis of gadolinium doped CdTe quantum dots with dual imaging modalities.

    PubMed

    Jiang, Chunli; Shen, Zhitao; Luo, Chunhua; Lin, Hechun; Huang, Rong; Wang, Yiting; Peng, Hui

    2016-08-01

    A facile one-pot strategy has been developed for the aqueous synthesis of Gd doped CdTe (Gd:CdTe) QDs as fluorescence and magnetic resonance imaging dual-modal agent. The prepared Gd:CdTe QDs showed narrow size distribution and the average size was less than 5nm. The amount of Gd(3+) dopant in Gd:CdTe QDs significantly affected the optical properties of obtained QDs. The highest PL QY for the prepared Gd:CdTe QDs was up to 42.5%. The QDs showed the weak toxicity and significant enhancement in MRI signal. The specific relaxivity value (r1) was determined to be 4.22mM(-1)s(-1). These properties make the prepared Gd:CdTe QDs be an effective dual-modal imaging agent and have great potential applications in biomedical field. PMID:27216651

  10. The Numerical Investigation of a Dual-Mode Scramjet Combustor

    NASA Technical Reports Server (NTRS)

    Riggins, David

    1998-01-01

    A numerical investigation of a multiple-jet array dual-mode scramjet combustor has been performed utilizing a three-dimensional Navier-Stokes code with finite-rate chemistry. Results indicate substantial upstream interaction in the form of an oblique shock/expansion train upstream of the combustor, culminating in completely subsonic flow in the vicinity of fuel injectors. The flow returns to supersonic velocities in the downstream (diverging) portion of the combustor. Mixing and combustion are rapid in this flow and predicted combustion efficiency closely matches experimental data. However, comparisons of wall pressure between the simulation and the experiment show i) substantial underprediction of the upstream interaction distance and ii) moderate overprediction of peak pressure in the vicinity of the entrance of the combustor. This can be at least partially explained by examination of available experimental data; this data shows a very significant movement of the entering vitiated airflow to the sides of the combustor (around the injector array and the upstream interaction front as a whole). This important effect is currently being examined by an extension of the modeling to include the entire half-duct of the same combustor geometry.

  11. Technology requirements for advanced earth-orbital transportation systems, dual-mode propulsion

    NASA Technical Reports Server (NTRS)

    Haefeli, R. C.; Littler, E. G.; Hurley, J. B.; Winter, M. G.

    1977-01-01

    The application of dual-mode propulsion concepts to fully reusable single-stage-to-orbit (SSTO) vehicles is discussed. Dual-mode propulsion uses main rocket engines that consume hydrocarbon fuels as well as liquid hydrogen fuel. Liquid oxygen is used as the oxidizer. These engine concepts were integrated into transportation vehicle designs capable of vertical takeoff, delivering a payload to earth orbit, and return to earth with a horizontal landing. Benefits of these vehicles were assessed and compared with vehicles using single-mode propulsion (liquid hydrogen and oxygen engines). Technology requirements for such advanced transportation systems were identified. Figures of merit, including life-cycle cost savings and research costs, were derived for dual-mode technology programs, and were used for assessments of potential benefits of proposed technology activities. Dual-mode propulsion concepts display potential for significant cost and performance benefits when applied to SSTO vehicles.

  12. Dual-mode operation of flexible piezoelectric polymer diaphragm for intracranial pressure measurement

    NASA Astrophysics Data System (ADS)

    Li, Chunyan; Wu, Pei-Ming; Shutter, Lori A.; Narayan, Raj K.

    2010-02-01

    The dual-mode operation of a polyvinylidene fluoride trifluoroethylene (PVDF-TrFE) piezoelectric polymer diaphragm, in a capacitive or resonant mode, is reported as a flexible intracranial pressure (ICP) sensor. The pressure sensor using a capacitive mode exhibits a higher linearity and less power consumption than resonant mode operated pressure sensor. In contrast, the latter provides better sensitivity and easier adaption for wireless application. The metrological properties of the dual-mode ICP sensor being described are satisfactory in vitro. We propose that the piezoelectric polymer diaphragm has a promising future in intracranial pressure monitoring.

  13. Dual-mode characteristics of the Buneman instability in a bounded slab plasma

    SciTech Connect

    Hong, Woo-Pyo; Jung, Young-Dae

    2015-06-15

    The dual-mode characteristics of the Buneman instability are investigated in a slab plasma, including the geometric effects. The dual symmetric and anti-symmetric dispersion modes of the Buneman instability are obtained by the plasma dielectric function with the spectral reflection conditions for the slab geometry. The result shows that the magnitudes of the growth rate for the symmetric mode are always greater than those for the anti-symmetric mode. It is also found that the geometric effect suppresses the position of the maximum growth rate for the Buneman instability in bounded slab plasmas since the maximum conditions for the symmetric and anti-symmetric modes of the Buneman instability are given by 0.60dual modes of the Buneman instability are also discussed.

  14. Design of a multistage depressed collector for the F-16 radar dual mode transmitter tube

    NASA Technical Reports Server (NTRS)

    Dayton, J. A., Jr.

    1982-01-01

    The design of a multistage depressed collector (MDC) for use with the F-16 radar dual mode transmitter tube is described. The methods employed and the rationale on which the design is based are presented.

  15. Technology requirements for advanced earth orbital transportation systems. Volume 3: Summary report - dual mode propulsion

    NASA Technical Reports Server (NTRS)

    Hepler, A. K.; Bangsund, E. L.

    1978-01-01

    The impact of dual-mode propulsion on cost-effective technology requirements for advanced earth-orbital transportation systems is considered. Additional objectives were to determine the advantages of the best dual mode concept relative to the LO2/LH2 concept of the basic study. Normal technology requirements applicable to horizontal take-off and landing single-stage-to-orbit systems utilizing dual mode rocket propulsion were projected to the 1985 time period. These technology projections were then incorporated in a vehicle parametric design analysis for two different operational concepts of a dual mode propulsion system. The resultant performance, weights and costs of each concept were compared. The selected propulsion concept was evaluated to confirm the parametric trending/scaling of weights and to optimize the configuration.

  16. Difference frequency modulation of multi-section dual-mode lasers with nanoscale surface gratings

    NASA Astrophysics Data System (ADS)

    Uusitalo, Topi; Virtanen, Heikki; Viheriälä, Jukka; Salmi, Joel; Aho, Antti T.; Dumitrescu, Mihail

    2016-03-01

    Dual-mode multi-section quantum-well distributed feedback lasers with surface gratings have been fabricated, without regrowth, at 1310 and 1550 nm using UV nano-imprint lithography. Several laser and grating sections have been employed to control and stabilize the dual-mode emission and to reduce mode competition. Frequency differences between 15 GHz and 1 THz were achieved for different longitudinal structures. Frequency difference variations of several GHz have been measured under bias modulation with rates up to a few GHz. Higher frequency difference modulation rates are expected from improved measurement setups and from employing quantum dot active regions for further reduction of mode competition.

  17. Comparison of dual-photon absorptiometry systems for total-body bone and soft tissue measurements: Dual-energy X-rays versus gadolinium 153

    SciTech Connect

    Russell-Aulet, M.; Wang, J.; Thornton, J.; Pierson, R.N. Jr. )

    1991-04-01

    A total of 81 subjects (41 males and 40 females) were scanned by dual-photon absorptiometry by 153Gd source (DPA; Lunar DP4) and by dual-energy x-ray absorptiometry (DEXA; Lunar-DPX) within a 24 h period. Total-body bone mineral density (TBMD), calcium content (Ca), and soft tissue mass (ST) were determined with a precision of about 1-1.5% using DPA and 0.5-1.0% using DEXA. Measurements of TBMD, Ca, ST, bone area (area), percentage fat, and regional bone mineral densities (BMD) were compared. Paired t-tests showed small but significant differences between all measurements. Correlations (r) for TBMD, Ca, area, ST, percentage fat, arm BMD, leg BMD, and trunk BMD were 0.99, 0.99, 0.97, 0.99, 0.97, 0.99, 0.99, and 0.98. There were small systematic differences for TBMD (less than 1%), calcium (3%), bone area (3%), soft tissue mass (7%), and percentage fat (9%) between the two approaches. Regression equations are given relating these measurements.

  18. Adaptive Transthoracic Refocusing of Dual-Mode Ultrasound Arrays

    PubMed Central

    Casper, Andrew J.; Wan, Yayun; Ebbini, Emad S.

    2010-01-01

    We present experimental validation results of an adaptive, image-based refocusing algorithm of dual-mode ultrasound arrays (DMUAs) in the presence of strongly scattering objects. This study is motivated by the need to develop noninvasive techniques for therapeutic targeting of tumors seated in organs where the therapeutic beam is partially obstructed by the ribcage, e.g., liver and kidney. We have developed an algorithm that takes advantage of the imaging capabilities of DMUAs to identify the ribs and the intercostals within the path of the therapeutic beam to produce a specified power deposition at the target while minimizing the exposure at the rib locations. This image-based refocusing algorithm takes advantage of the inherent registration between the imaging and therapeutic coordinate systems of DMUAs in the estimation of array directivity vectors at the target and rib locations. These directivity vectors are then used in solving a constrained optimization problem allowing for adaptive refocusing, directing the acoustical energy through the intercostals, and avoiding the rib locations. The experimental validation study utilized a 1-MHz, 64-element DMUA in focusing through a block of tissue-mimicking phantom [0.5 dB/(cm·MHz)] with embedded Plexiglas ribs. Single transmit focus (STF) images obtained with the DMUA were used for image-guided selection of the critical and target points to be used for adaptive refocusing. Experimental results show that the echogenicity of the ribs in STF images provide feedback on the reduction of power deposition at rib locations. This was confirmed by direct comparison of measured temperature rise and integrated backscatter at the rib locations. Direct temperature measurements also confirm the improved power deposition at the target and the reduction in power deposition at the rib locations. Finally, we have compared the quality of the image-based adaptive refocusing algorithm with a phase-conjugation solution obtained by direct

  19. Dispersion-compensating dual-mode optical fibers desirable for erbium-doped-fiber-amplified systems

    SciTech Connect

    Eguchi, Masashi

    2001-06-01

    A broadband dispersion-compensating dual-mode optical fiber with a double-layer profile core is proposed to compensate for positive dispersion in conventional single-mode optical fibers operating near 1.55 {mu}m. This wavelength band is suitable for erbium-doped-fiber-amplified systems. It is known that the first higher-order mode of dual-mode fibers exhibits large negative waveguide dispersion, and double-layer profile core fibers are dispersion-shifted fibers whose transmission and bending losses are lower than those of simple core-cladding dispersion-shifted fibers. Such advantages are attractive for commercial devices or modules. Here, a dispersion-compensating dual-mode fiber with a double-layer profile core that satisfies both low bending loss and broadband dispersion compensation is proposed. {copyright} 2001 Optical Society of America

  20. A Preliminary Cost Study of the Dual Mode Inverter Controller

    SciTech Connect

    McKeever, J.W.

    2005-01-28

    In 1998, the Power Electronics and Electric Machinery Research Center (PEEMRC) at the Oak Ridge National Laboratory (ORNL) started a program to investigate alternate field weakening schemes for permanent magnet (PM) motors. The adjective ''alternate'' was used because at that time, outside research emphasis was on motors with interior-mounted PMs (IPMs). The PEEMRC emphasis was placed on motors with surface-mounted PMs (SPMs) because of the relative ease of manufacturing SPM motors compared with the IPM motors. Today the PEEMRC is continuing research on SPMs while examining the IPMs that have been developed by industry. Out of this task--the goal of which was to find ways to drive PM motors that inherently have low inductance at high speeds where their back-emf exceeds the supply voltage--ORNL developed and demonstrated the dual mode inverter control (DMIC) [1,2] method of field weakening for SPM motors. The predecessor of DMIC is conventional phase advance (CPA), which was developed by UQM Technologies, Inc. [3]. Fig. 1 shows the three sets of anti-parallel thyristors in the dashed box that comprise the DMIC. If one removes the dashed box by shorting each set of anti-parallel thyristors, the configuration becomes a conventional full bridge inverter on the left driving a three phase motor on the right. CPA may be used to drive this configuration ORNL's initial analyses of CPA and DMIC were based on driving motors with trapezoidal back-emfs [4-6], obtained using double layer lapped stator windings with one slot per pole per phase. A PM motor with a sinusoidal back-emf obtained with two poles per slot per phase has been analyzed under DMIC operation as a University of Tennessee-Knoxville (UTK) doctoral dissertation [7]. In the process of this research, ORNL has completed an analysis that explains and quantifies the role of inductance in these methods of control. The Appendix includes information on the equations for the three components of phase inductance, L{sub gap

  1. An engineering treatise on the CARE II dual mode and coverage models

    NASA Technical Reports Server (NTRS)

    1976-01-01

    A mathematical model used to calculate the reliability of any dual-mode, spare-switching computer system was described, and some illustrative examples were presented. The possibility of extending the resultant computer program further was also examined, enabling it, in particular, to accommodate computer configurations involving more than two modes of operation.

  2. Dual-mode type algorithms for blind equalization

    NASA Astrophysics Data System (ADS)

    Weerackody, Vijitha; Kassam, Saleem A.

    1994-01-01

    Adaptive channel equalization accomplished without resorting to a training sequence is known as blind equalization. The Godard algorithm and the generalized Sato algorithm are two widely referenced algorithms for blind equalization of a QAM system. These algorithms exhibit very slow convergence rates when compared to algorithms employed in conventional data-aided equalization schemes. In order to speed up the convergence process, these algorithms may be switched over to a decision-directed equalization scheme once the error level is reasonably low. We present a scheme which is capable of operating in two modes: blind equalization mode and a mode similar to the decision-directed equalization mode. In this proposed scheme, the dominant mode of operation changes from the blind equalization mode at higher error levels to the mode similar to the decision-directed equalization mode at lower error levels. Manual switch-over to the decision-directed mode from the blind equalization mode, or vice-versa, is not necessary since transitions between the two modes take place smoothly and automatically.

  3. Dual-mode waveguides for variably polarised slotted waveguide array antennas

    NASA Astrophysics Data System (ADS)

    Sangster, A. J.; Lyon, R. W.

    1980-10-01

    The polarization selection mechanism in dual-mode slotted waveguide arrays requires that the exciting modes of the waveguide exhibit essentially identical phase and group velocities. This generally implies using an even and an odd mode of the structure, in an arrangement which provides useable current distributions in the slotted wall. This paper describes the results of a study of some waveguide configurations aimed at meeting these requirements in an array which was additionally intended to be frequency scanned.

  4. Thermodynamic Analysis of Dual-Mode Scramjet Engine Operation and Performance

    NASA Technical Reports Server (NTRS)

    Riggins, David; Tacket, Regan; Taylor, Trent; Auslender, Aaron

    2006-01-01

    Recent analytical advances in understanding the performance continuum (the thermodynamic spectrum) for air-breathing engines based on fundamental second-law considerations have clarified scramjet and ramjet operation, performance, and characteristics. Second-law based analysis is extended specifically in this work to clarify and describe the performance characteristics for dual-mode scramjet operation in the mid-speed range of flight Mach 4 to 7. This is done by a fundamental investigation of the complex but predictable interplay between heat release and irreversibilities in such an engine; results demonstrate the flow and performance character of the dual mode regime and of dual mode transition behavior. Both analytical and computational (multi-dimensional CFD) studies of sample dual-mode flow-fields are performed in order to demonstrate the second-law capability and performance and operability issues. The impact of the dual-mode regime is found to be characterized by decreasing overall irreversibility with increasing heat release, within the operability limits of the system.

  5. Tuning the relaxation rates of dual-mode T1/T2 nanoparticle contrast agents: a study into the ideal system

    NASA Astrophysics Data System (ADS)

    Keasberry, Natasha A.; Bañobre-López, Manuel; Wood, Christopher; Stasiuk, Graeme. J.; Gallo, Juan; Long, Nicholas. J.

    2015-09-01

    Magnetic resonance imaging (MRI) is an excellent imaging modality. However the low sensitivity of the technique poses a challenge to achieving an accurate image of function at the molecular level. To overcome this, contrast agents are used; typically gadolinium based agents for T1 weighted imaging, or iron oxide based agents for T2 imaging. Traditionally, only one imaging mode is used per diagnosis although several physiological situations are known to interfere with the signal induced by the contrast agents in each individual imaging mode acquisition. Recently, the combination of both T1 and T2 imaging capabilities into a single platform has emerged as a tool to reduce uncertainties in MR image analysis. To date, contradicting reports on the effect on the contrast of the coupling of a T1 and T2 agent have hampered the application of these specialised probes. Herein, we present a systematic experimental study on a range of gadolinium-labelled magnetite nanoparticles envisioned to bring some light into the mechanism of interaction between T1 and T2 components, and advance towards the design of efficient (dual) T1 and T2 MRI probes. Unexpected behaviours observed in some of the constructs will be discussed. In this study, we demonstrate that the relaxivity of such multimodal probes can be rationally tuned to obtain unmatched potentials in MR imaging, exemplified by preparation of the magnetite-based nanoparticle with the highest T2 relaxivity described to date.Magnetic resonance imaging (MRI) is an excellent imaging modality. However the low sensitivity of the technique poses a challenge to achieving an accurate image of function at the molecular level. To overcome this, contrast agents are used; typically gadolinium based agents for T1 weighted imaging, or iron oxide based agents for T2 imaging. Traditionally, only one imaging mode is used per diagnosis although several physiological situations are known to interfere with the signal induced by the contrast agents in

  6. Engine performance analysis and optimization of a dual-mode scramjet with varied inlet conditions

    NASA Astrophysics Data System (ADS)

    Tian, Lu; Chen, Li-Hong; Chen, Qiang; Zhong, Feng-Quan; Chang, Xin-Yu

    2016-02-01

    A dual-mode scramjet can operate in a wide range of flight conditions. Higher thrust can be generated by adopting suitable combustion modes. Based on the net thrust, an analysis and preliminary optimal design of a kerosene-fueled parameterized dual-mode scramjet at a crucial flight Mach number of 6 were investigated by using a modified quasi-one-dimensional method and simulated annealing strategy. Engine structure and heat release distributions, affecting the engine thrust, were chosen as analytical parameters for varied inlet conditions (isolator entrance Mach number: 1.5-3.5). Results show that different optimal heat release distributions and structural conditions can be obtained at five different inlet conditions. The highest net thrust of the parameterized dual-mode engine can be achieved by a subsonic combustion mode at an isolator entrance Mach number of 2.5. Additionally, the effects of heat release and scramjet structure on net thrust have been discussed. The present results and the developed analytical method can provide guidance for the design and optimization of high-performance dual-mode scramjets.

  7. An investigation of dual-mode operation of a nuclear-thermal rocket engine

    SciTech Connect

    Kirk, W.L.; Hedstrom, J.C.; Moore, S.W.; McFarland, R.D.; Merrigan, M.A.; Buksa, J.J.; Cappiello, M.W.; Hanson, D.L.; Woloshun, K.A.

    1991-06-01

    A preliminary assessment of the technical feasibility and mass competitiveness of a dual-mode nuclear propulsion and power system based on Rover-type reactors has been completed. Earlier studies have indicated that dual-mode systems appear attractive for electrical power levels of a few kilowatts. However, at the megawatt electrical power level considered in this study, it appears that extensive modifications to the nuclear-thermal engines would be required, the feasibility of which is unclear. Mass competitiveness at high electrical power levels is also uncertain. Further study of reactor and shield design in conjuction with mission and vehicle studies is necessary in order to determine a useful dual-mode power range. 9 refs., 20 figs., 4 tabs.

  8. Dual sensitivity mode system for monitoring processes and sensors

    DOEpatents

    Wilks, Alan D.; Wegerich, Stephan W.; Gross, Kenneth C.

    2000-01-01

    A method and system for analyzing a source of data. The system and method involves initially training a system using a selected data signal, calculating at least two levels of sensitivity using a pattern recognition methodology, activating a first mode of alarm sensitivity to monitor the data source, activating a second mode of alarm sensitivity to monitor the data source and generating a first alarm signal upon the first mode of sensitivity detecting an alarm condition and a second alarm signal upon the second mode of sensitivity detecting an associated alarm condition. The first alarm condition and second alarm condition can be acted upon by an operator and/or analyzed by a specialist or computer program.

  9. Coupling Single-Mode Fiber to Uniform and Symmetrically Tapered Thin-Film Waveguide Structures Using Gadolinium Gallium Garnet

    NASA Technical Reports Server (NTRS)

    Gadi, Jagannath; Yalamanchili, Raj; Shahid, Mohammad

    1995-01-01

    The need for high efficiency components has grown significantly due to the expanding role of fiber optic communications for various applications. Integrated optics is in a state of metamorphosis and there are many problems awaiting solutions. One of the main problems being the lack of a simple and efficient method of coupling single-mode fibers to thin-film devices for integrated optics. In this paper, optical coupling between a single-mode fiber and a uniform and tapered thin-film waveguide is theoretically modeled and analyzed. A novel tapered structure presented in this paper is shown to produce perfect match for power transfer.

  10. A transportable 50 kA dual mode lightning simulator

    NASA Technical Reports Server (NTRS)

    Salisbury, K.; Lloyd, S.; Chen, Y. G.

    1991-01-01

    A transportable lightning simulator was designed, built and tested, which is capable of delivering more than 50 kA to an 8 micro-H test object. The simulator was designed to be a versatile device in the lightning laboratory while meeting the requirements of MIL-STD-1757A for component E current waveforms. The system is capable of operating in either a ringing mode with a Q greater than 5 and a nominal frequency of 160 kHz, or a unipolar mode with no hardware configuration changes. The ringing mode is obtained by the LCR series circuit formed by the pulse generator and test object. The unipolar mode is obtained by closing an electrically triggered crowbar switch at peak current. The simulator exceeds the peak current requirement and rate of rise requirements for MIL-STD-1757A in both the ringing and unipolar modes. The pulse half width in the unipolar mode is in excess of 50 microsec and the action is in excess of 10(exp 5) A(exp 2)s. The design, component values, and test results are presented.

  11. Teeter-totter effect of terahertz dual modes in C-shaped complementary split-ring resonators

    NASA Astrophysics Data System (ADS)

    Song, Zhiqiang; Zhao, Zhenyu; Zhao, Hongwei; Peng, Wei; He, Xiaoyong; Shi, Wangzhou

    2015-07-01

    A teeter-totter effect of terahertz (THz) resonant modes in C-shaped complementary split-ring resonators (CSRRs) is observed. The dual resonant mode transmission enhancement was investigated using THz time-domain spectroscopy. The intensity of the lower-frequency resonance modes increases monotonically with the CSSR gap width, which is accompanied by a monotonic decrease in the intensity of the higher-frequency resonance modes. The origin of the dual resonant modes is numerically explained by the electromagnetic energy density distribution and surface current analysis. The inductive-capacitive resonance dominates the lower frequency mode, while the dipole oscillation dominates the higher frequency mode. By tuning the gap of the CSRR, an equilibrant transmittance of above dual resonance modes can be designed. This teeter-totter effect promises a possible application of CSSRs as potential dual-bandpass filters in the THz-region.

  12. An overmoded relativistic backward wave oscillator with efficient dual-mode operation

    SciTech Connect

    Xiao, Renzhen; Li, Jiawei; Bai, Xianchen; Song, Zhimin; Teng, Yan; Ye, Hu; Li, Xiaoze; Sun, Jun; Chen, Changhua; Zhang, Xiaowei

    2014-03-03

    A dual-mode operation mechanism in an overmoded relativistic backward wave oscillator is presented. The electron beam interacts with the −1st space harmonic of TM{sub 01} mode synchronously in the slow wave structure. Then the backward propagating TM{sub 01} mode is converted to the forward propagating TM{sub 02} mode. As the phase velocity of the volume harmonic of TM{sub 02} mode is about twice that of the surface harmonic of TM{sub 01} mode, the TM{sub 02} mode also plays an important role in the high-power microwave generation. Particle-in-cell simulation shows that an efficiency of 48% and a significant improvement of the power capacity have been obtained.

  13. Integrated dual-mode 3 dB power coupler based on tapered directional coupler

    PubMed Central

    Luo, Yuchan; Yu, Yu; Ye, Mengyuan; Sun, Chunlei; Zhang, Xinliang

    2016-01-01

    A dual-mode 3 dB power coupler based on silicon-on-insulator platform for mode division multiplexing system is proposed and demonstrated. The device, which consists of a tapered directional coupler and two output bend waveguides, has a 50:50 coupling ratio around the wavelength of 1550 nm for both fundamental and first order transverse magnetic (TM0 and TM1) modes. Based on asymmetrical tapered structure, a short common coupling length of ~15.2 μm for both modes is realized by optimizing the width of the tapered waveguide. The measured insertion loss for both modes is less than 0.7 dB. The crosstalks are about −14.3 dB for TM0 mode and −18.1 dB for TM1 mode. PMID:27002747

  14. Integrated dual-mode 3 dB power coupler based on tapered directional coupler.

    PubMed

    Luo, Yuchan; Yu, Yu; Ye, Mengyuan; Sun, Chunlei; Zhang, Xinliang

    2016-01-01

    A dual-mode 3 dB power coupler based on silicon-on-insulator platform for mode division multiplexing system is proposed and demonstrated. The device, which consists of a tapered directional coupler and two output bend waveguides, has a 50:50 coupling ratio around the wavelength of 1550 nm for both fundamental and first order transverse magnetic (TM0 and TM1) modes. Based on asymmetrical tapered structure, a short common coupling length of ~15.2 μm for both modes is realized by optimizing the width of the tapered waveguide. The measured insertion loss for both modes is less than 0.7 dB. The crosstalks are about -14.3 dB for TM0 mode and -18.1 dB for TM1 mode. PMID:27002747

  15. Research Study to Identify Technology Requirements for Advanced Earth-Orbital Transportation Systems, Dual-Mode Propulsion

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The results of a study of dual mode propulsion concepts applied to advanced earth orbital transportation systems using reuseable single stage to orbit vehicle concepts were summarized. Both series burn and parallel burn modes of propulsion were analyzed for vertical takeoff, horizontal landing vehicles based on accelerated technology goals. A major study objective was to assess the merits of dual mode main propulsion concepts compared to single mode concepts for carrying payloads of Space Shuttle type to orbit.

  16. Short monolithic dual-wavelength single-longitudinal-mode DBR phosphate fiber laser.

    PubMed

    Xiong, Lingyun; Hofmann, Peter; Schülzgen, Axel; Peyghambarian, N; Albert, Jacques

    2014-06-20

    We propose and demonstrate a 5-cm-long monolithic dual-wavelength single-longitudinal mode distributed Bragg reflector (DBR) all-phosphate fiber laser. Strong UV-induced fiber Bragg gratings are directly written in highly Er/Yb codoped phosphate fiber. The separation between gratings is selected as 1 cm to only excite two longitudinal modes in the DBR cavity. By exploiting the spatial hole burning effect and the polarization hole burning effect, stable narrow-linewidth dual-wavelength lasing emission with 38 pm wavelength spacing and a total emitted power of 2.8 mW is obtained from this DBR fiber laser. A microwave signal at 4.58 GHz is generated by the heterodyne detection of the dual-wavelength laser. PMID:24979414

  17. Mode-Area Scaling of Helical-Core Dual-Clad Fiber Lasers and Amplifiers

    SciTech Connect

    Jiang, Z.; Marciante, J.R.

    2005-09-30

    Helical-core, dual-clad fibers have been designed for single-mode operation with 60-um cores and 0.10 NA. Helical fibers are shown to perform where conventional coiled fibers cannot operate, with possible scaling to 200-um-diameter helical cores.

  18. A dual-mode proximity sensor with integrated capacitive and temperature sensing units

    NASA Astrophysics Data System (ADS)

    Qiu, Shihua; Huang, Ying; He, Xiaoyue; Sun, Zhiguang; Liu, Ping; Liu, Caixia

    2015-10-01

    The proximity sensor is one of the most important devices in the field of robot application. It can accurately provide the proximity information to assistant robots to interact with human beings and the external environment safely. In this paper, we have proposed and demonstrated a dual-mode proximity sensor composed of capacitive and resistive sensing units. We defined the capacitive type proximity sensor perceiving the proximity information as C-mode and the resistive type proximity sensor detecting as R-mode. Graphene nanoplatelets (GNPs) were chosen as the R-mode sensing material because of its high performance. The dual-mode proximity sensor presents the following features: (1) the sensing distance of the dual-mode proximity sensor has been enlarged compared with the single capacitive proximity sensor in the same geometrical pattern; (2) experiments have verified that the proposed sensor can sense the proximity information of different materials; (3) the proximity sensing capability of the sensor has been improved by two modes perceive collaboratively, for a plastic block at a temperature of 60 °C: the R-mode will perceive the proximity information when the distance d between the sensor and object is 6.0-17.0 mm and the C-mode will do that when their interval is 0-2.0 mm additionally two modes will work together when the distance is 2.0-6.0 mm. These features indicate our transducer is very valuable in skin-like sensing applications.

  19. Ultranarrow dual-transmission-band fiber Bragg grating filter and its application in a dual-wavelength single-longitudinal-mode fiber ring laser.

    PubMed

    Chen, Xiangfei; Yao, Jianping; Deng, Zhichao

    2005-08-15

    A fiber Bragg grating filter with ultranarrow dual-transmission bands implemented using the equivalent phase shift technique is demonstrated. A fiber ring laser that incorporates a dual-transmission-band fiber Bragg grating filter in the ring cavity is implemented. Dual-wavelength single-longitudinal-mode lasing with a wavelength spacing as small as 0.147 nm at room temperature is experimentally demonstrated. PMID:16127912

  20. Accurate Analysis and Computer Aided Design of Microstrip Dual Mode Resonators and Filters.

    NASA Astrophysics Data System (ADS)

    Grounds, Preston Whitfield, III

    1995-01-01

    Microstrip structures are of interest due to their many applications in microwave circuit design. Their small size and ease of connection to both passive and active components make them well suited for use in systems where size and space is at a premium. These include satellite communication systems, radar systems, satellite navigation systems, cellular phones and many others. In general, space is always a premium for any mobile system. Microstrip resonators find particular application in oscillators and filters. In typical filters each microstrip patch corresponds to one resonator. However, when dual mode patches are employed, each patch acts as two resonators and therefore reduces the amount of space required to build the filter. This dissertation focuses on the accurate electromagnetic analysis of the components of planar dual mode filters. Highly accurate analyses are required so that the resonator to resonator coupling and the resonator to input/output can be predicted with precision. Hence, filters can be built with a minimum of design iterations and tuning. The analysis used herein is an integral equation formulation in the spectral domain. The analysis is done in the spectral domain since the Green's function can be derived in closed form, and the spatial domain convolution becomes a simple product. The resulting set of equations is solved using the Method of Moments with Galerkin's procedure. The electromagnetic analysis is applied to range of problems including unloaded dual mode patches, dual mode patches coupled to microstrip feedlines, and complete filter structures. At each step calculated results are compared to measured results and good agreement is found. The calculated results are also compared to results from the circuit analysis program HP EESOF^{ rm TM} and again good agreement is found. A dual mode elliptic filter is built and good performance is obtained.

  1. Analysis of dual-mode lasing characteristics in a 1310-nm optically injected quantum dot distributed feedback laser

    NASA Astrophysics Data System (ADS)

    Raghunathan, R.; Olinger, J.; Hurtado, A.; Grillot, F.; Kovanis, V.; Lester, L. F.

    2015-03-01

    Recent work has shown the Quantum Dot (QD) material system to be well-suited to support dual-mode lasing. In particular, optical injection from a master laser (ML) into the residual Fabry-Perot (FP) modes of a 1310 nm Quantum Dot Distributed Feedback (QD-DFB) laser has been recently demonstrated to offer a highly reliable platform for stable dual-mode lasing operation. External controls on the ML, such as operating temperature and bias current, can be used to precisely adjust the spacing between the two lasing modes. This tunability of modeseparation is very promising for a range of applications requiring the generation of microwave, millimeter wave and terahertz signals. Considering the versatility and utility of such a scheme, it is imperative to acquire a deeper understanding of the factors that influence the dual-mode lasing process, in order to optimize performance. Toward this end, this paper seeks to further our understanding of the optically-injected dual-mode lasing mechanism. For fixed values of optical power injected into each FP residual mode and wavelength detuning, the dual-mode lasing characteristics are analyzed with regard to important system parameters such as the position and the intensity of the injected residual mode (relative to the Bragg and the other residual FP modes of the device) for two similarly-fabricated QD-DFBs. Results indicate that for dual mode lasing spaced less than 5 nm apart, the relative intensity of the injected FP mode and intracavity noise levels are critical factors in determining dual mode lasing behavior. Insight into the dual-mode lasing characteristics could provide an important design guideline for the master and QD-DFB slave laser cavities.

  2. Dual collection mode optical microscope with single-pixel detection

    NASA Astrophysics Data System (ADS)

    Rodríguez, A. D.; Clemente, P.; Fernández-Alonso, Mercedes; Tajahuerce, E.; Lancis, J.

    2015-07-01

    In this work we have developed a single-pixel optical microscope that provides both re ection and transmission images of the sample under test by attaching a diamond pixel layout DMD to a commercial inverted microscope. Our system performs simultaneous measurements of re ection and transmission modes. Besides, in contrast with a conventional system, in our single-element detection system both images belong, unequivocally, to the same plane of the sample. Furthermore, we have designed an algorithm to modify the shape of the projected patterns that improves the resolution and prevents the artifacts produced by the diamond pixel architecture.

  3. A Dual-Mode Actinic EUV Mask Inspection Tool

    SciTech Connect

    Liu, Y; Barty, A; Gullikson, E; S.Taylor, J; Liddle, J A; Wood, O

    2005-03-21

    To qualify the performance of non-actinic inspection tools, a novel EUV mask inspection system has been installed at the Advanced Light Source (ALS) synchrotron facility at Lawrence Berkeley National Laboratory. Similar to the older generation actinic mask inspection tool, the new system can operate in scanning mode, when mask blanks are scanned for defects using 13.5-nm in-band radiation to identify and map all locations on the mask that scatter a significant amount of EUV light. By modifying and optimizing beamline optics (11.3.2 at ALS) and replacing K-B focusing mirrors with a high quality Schwarzschild illuminator, the new system achieves an order of magnitude improvement on in-band EUV flux density at the mask, enabling faster scanning speed and higher sensitivity to smaller defects. Moreover, the system can also operate in imaging mode, when it becomes a zone-plate-based full-field EUV microscope with spatial resolution better than 100 nm. The microscope utilizes an off-axis setup, making it possible to obtain bright field images over a field-of-view of 5 x 5 {micro}m.

  4. Dual fragmentation modes of the explosively dispersed granular materials.

    PubMed

    Xue, Kun; Yu, Qiqi; Bai, Chunhua

    2014-09-01

    Granular materials subjected to blast loading caused by a central explosion exhibit a distinctive dual jetting phenomenon. A large number of fine particle jets are ejected from the outer edge of the charge upon the reflection of the shock wave from the free surface, and are soon overtaken and overlapped by a second set of much thicker particle jets from the inner edge. Our numerical studies suggest that these two distinct sets of particle jets arise from a subsequent fragmentation of the outer and inner particle layers formed during shock interaction. The instability onset of the inner particle layer, which remains intact after the spallation of the outer particle layer, corresponds to the destabilizing viscous forces prevailing over the stabilizing inertial forces. The physical mechanism responsible for the spallation of the outer particle layer is accounted for by a three-phase cavitation model consisting of nucleation, unconditioned and conditioned growth of voids. The theoretically predicted fragmentation onset and fragment size are well consistent with the experimental results. Moreover, by incorporating the moisture effect into the granular material model, results of the cavitation model indicate an increased number of jets generated by saturated particles, as observed in experiments. With minor shock energy being consumed on the saturated particle compaction thanks to the remarkably low compressibility of saturated particles, the shock wave retains the steep front during propagation and subsequently produces a sharp reflection wave leading to a considerably higher strain relaxation rate in saturated particles than that in dry particles. The pressure relaxation duration prescribes the time the activated nucleation sites are allowed to communicate with each other. Consequently nucleation sites in saturated particles have more chances to survive and fully develop than those in dry particles giving rise to smaller fragments. PMID:25260327

  5. Analysis method and principle of dual-mode electro-mechanical variable transmission program

    NASA Astrophysics Data System (ADS)

    Li, Hongcai; Yan, Qingdong; Xiang, Changle; Wang, Weida

    2012-05-01

    Automotive industry, as an important pillar of the national economy, has been rapidly developing in recent years. But proplems such as energy comsumption and environmental pollution are posed at the same time. Electro-mechanical variable transmission system is considered one of avilable workarounds. It is brought forward a kind of design methods of dual-mode electro-mechanical variable transmission system rotational speed characteristics and dual-mode drive diagrams. With the motor operating behavior of running in four quadrants and the speed characteristics of the simple internal and external meshing single planetary gear train, four kinds of dual-mode electro-mechanical transmission system scheme are designed. And the velocity, torque and power characteristics of one of the programs are analyzed. The magnitude of the electric split-flow power is an important factor which influences the system performance, so in the parameters matching design, it needs to reduce the power needs under the first mode of the motor. The motor, output rotational speed range and the position of the mode switching point have relationships with the characteristics design of the planetary gear set. The analysis method is to provide a reference for hybrid vehicles' design. As the involved rotational speed and torque relationships are the natural contact of every part of transmission system, a theory basis of system program and performance analysis is provided.

  6. A Priori Analysis of Flamelet-Based Modeling for a Dual-Mode Scramjet Combustor

    NASA Technical Reports Server (NTRS)

    Quinlan, Jesse R.; McDaniel, James C.; Drozda, Tomasz G.; Lacaze, Guilhem; Oefelein, Joseph

    2014-01-01

    An a priori investigation of the applicability of flamelet-based combustion models to dual-mode scramjet combustion was performed utilizing Reynolds-averaged simulations (RAS). For this purpose, the HIFiRE Direct Connect Rig (HDCR) flowpath, fueled with a JP-7 fuel surrogate and operating in dual- and scram-mode was considered. The chemistry of the JP-7 fuel surrogate was modeled using a 22 species, 18-step chemical reaction mechanism. Simulation results were compared to experimentally-obtained, time-averaged, wall pressure measurements to validate the RAS solutions. The analysis of the dual-mode operation of this flowpath showed regions of predominately non-premixed, high-Damkohler number, combustion. Regions of premixed combustion were also present but associated with only a small fraction of the total heat-release in the flow. This is in contrast to the scram-mode operation, where a comparable amount of heat is released from non-premixed and premixed combustion modes. Representative flamelet boundary conditions were estimated by analyzing probability density functions for temperature and pressure for pure fuel and oxidizer conditions. The results of the present study reveal the potential for a flamelet model to accurately model the combustion processes in the HDCR and likely other high-speed flowpaths of engineering interest.

  7. Dual mode microwave tool for dielectric analysis and thermal ablation treatment of organic tissue.

    PubMed

    Puentes, Margarita; Bashir, Fahed; Schüssler, Martin; Jakoby, Rolf

    2012-01-01

    A dual mode tool design to analyze organic tissue and locally perform thermal ablation treatment is presented. The tool is made of an array of split-ring resonators. It can operate on a sensing mode to track the relative dielectric changes from the organic tissue and on a treatment mode to perform thermal ablation at different input powers. The measurements were done with phantoms of human tissue. The tool is able to focus a hot spot of approximately 0.2mm with a temperature of 109 °C at an input power of 10W. PMID:23366811

  8. Wavelength bistability based on optical injection in a novel tunable dual mode laser.

    PubMed

    Zhao, Hang; Zhu, Yao; Li, Feng; Yu, Yonglin

    2016-02-22

    A novel tunable dual mode laser is proposed based on a double-layer Bragg grating structure, named double-layer grating distributed Bragg reflector (DLG-DBR) laser. With controlling the gain saturation condition, different oscillating states can be observed. The nonlinear dynamics characteristics including bifurcation of the laser under optical injection with two different start-up sequences are analyzed with numerical simulations. Furthermore, we investigate the lasing wavelength bistability of the laser combined with its tuning characteristics theoretically. Optical memory operation based on the external optical injection locking bistability of the dual mode device is proposed. The memory operation can be achieved in the whole wavelength window with a 10 nm tuning range. A mode suppression ratio (MSR) of more than 45 dB is achieved between the two bistable states. PMID:26907035

  9. A Dual-Moded Cavity for RF Breakdown Studies

    SciTech Connect

    Nantista, Christopher; Adolphsen, Chris; Wang, Faya; /SLAC

    2010-08-25

    The phenomenon of rf breakdown presents a technological limitation in the application of high-gradient particle acceleration in normal conducting rf structures. Attempts to understand the onset of this phenomenon and to study its limits with different materials, cell shapes, and pulse widths has been driven in recent years by linear collider development. One question of interest is the role magnetic field plays relative to electric field. A design is presented for a single, nonaccelerating, rf cavity resonant in two modes, which, driven independently, allow the rf magnetic field to be increased on the region of highest electric field without affecting the latter. The design allows for the potential reuse of the cavity with different samples in the high-field region. High power data is not yet available.

  10. A PLANAR, RECTANGULAR WAVEGUIDE LAUNCHER AND EXTRACTOR FOR A DUAL-MODED RF POWER DISTRIBUTION SYSTEM

    SciTech Connect

    Nantista, Christopher D.

    2000-11-21

    The desire to reduce the amount of low-loss, circular-waveguide delay line required in a pulse-compressing power distribution system for the Next Linear Collider has led to the pursuit of multi-moded schemes [1]. In such a system, power is delivered to different destinations through the same waveguide via different propagating modes. Current plans [2] utilize two modes, with manipulations done primarily in overmoded rectangular guide. We describe two key components of the system, a four-input/four-output, dual-mode launcher and an extractor for diverting one mode from the delay line to an accelerator feed while allowing the other to pass on to an upstream feed. These novel passive waveguide devices utilize the rectangular TE10 and TE20 modes. Because they must carry up to 600 MW pulsed rf power, H-planar symmetry is maintained in their designs to allow the use of overheight waveguide, and features that invite breakdown, such as coupling slots, irises, and septa, are avoided. Special rectangular-to-circular tapers [3] will be used to convert between the above modes and the circular TE11{sup o} (TE12{sup o}) and TE01{sup o} delay line modes, respectively. Rectangular waveguide for relative ease of handling. Mode converters, including special cross-section tapers [3] will be used to transform between the above circular waveguide modes and the TE20 and TE10 rectangular waveguide modes, respectively.

  11. Exceptional points and asymmetric mode conversion in quasi-guided dual-mode optical waveguides

    PubMed Central

    Ghosh, S. N.; Chong, Y. D.

    2016-01-01

    Non-Hermitian systems host unconventional physical effects that be used to design new optical devices. We study a non-Hermitian system consisting of 1D planar optical waveguides with suitable amount of simultaneous gain and loss. The parameter space contains an exceptional point, which can be accessed by varying the transverse gain and loss profile. When light propagates through the waveguide structure, the output mode is independent of the choice of input mode. This “asymmetric mode conversion” phenomenon can be explained by the swapping of mode identities in the vicinity of the exceptional point, together with the failure of adiabatic evolution in non-Hermitian systems. PMID:27101933

  12. Exceptional points and asymmetric mode conversion in quasi-guided dual-mode optical waveguides

    NASA Astrophysics Data System (ADS)

    Ghosh, S. N.; Chong, Y. D.

    2016-04-01

    Non-Hermitian systems host unconventional physical effects that be used to design new optical devices. We study a non-Hermitian system consisting of 1D planar optical waveguides with suitable amount of simultaneous gain and loss. The parameter space contains an exceptional point, which can be accessed by varying the transverse gain and loss profile. When light propagates through the waveguide structure, the output mode is independent of the choice of input mode. This “asymmetric mode conversion” phenomenon can be explained by the swapping of mode identities in the vicinity of the exceptional point, together with the failure of adiabatic evolution in non-Hermitian systems.

  13. Dual extraction of R-mode and Q-mode factor solutions

    USGS Publications Warehouse

    Zhou, D.; Chang, T.; Davis, J.C.

    1983-01-01

    It is mathematically possible to extract both R-mode and Q-mode factors simultaneously (RQ-mode factor analysis)by invoking the Eckhart-Young theorem. The resulting factors will be expressed in measures determined by the form of the scalings that have been applied to the original data matrix. Unless the measures for both solutions are meaningful for the problem at hand, the factor results may be misleading or uninterpretable. Correspondence analysis uses a symmetrical scaling of both rows and columns to achieve measures of proportional similarity between objects and variables. In the literature, the resulting similarity is a ??2distance appropriate for analysis of enumerated data, the original application of correspondence analysis. Justification for the use of this measure with interval or ratio data is unconvincing, but a minor modification of the scaling procedure yields the profile similarity, which is an appropriate measure. Symmetrical scaling of rows and columns is unnecessary for RQ-mode factor analysis. If the data are scaled so the minor product W'W is the correlation matrix, the major product WW'is expressed in the Euclidean distances between objects. Therefore, RQ-mode factor analysis can be performed so that the R mode is a principal components solution and the Q mode is a principal coordinates solution. For applications where the magnitudes of differences are important, this approach will yield more interpretable results than will correspondence analysis. ?? 1983 Plenum Publishing Corporation.

  14. Novel Hexagonal Dual-Mode Substrate Integrated Waveguide Filter with Source-Load Coupling

    PubMed Central

    Zhang, Gen; Xu, Meijuan

    2014-01-01

    Hexagonal dual-mode cavity and its application to substrate integrated waveguide (SIW) filter are presented. The hexagonal SIW resonator which can combine flexibility of rectangular cavity and performance of circular cavity is convenient for dual-mode bandpass filters design. By introducing coupling between source and load, the filter not only has good selectivity due to two controllable transmission zeros, but also has a small size by the virtue of its single-cavity structure. A demonstration filter with a center frequency of 10 GHz and a 3 dB fractional bandwidth of 4% is designed and fabricated to validate the proposed structure. Measured results are in good agreement with simulated ones. PMID:24895669

  15. Novel hexagonal dual-mode substrate integrated waveguide filter with source-load coupling.

    PubMed

    Xu, Ziqiang; Zhang, Gen; Xia, Hong; Xu, Meijuan

    2014-01-01

    Hexagonal dual-mode cavity and its application to substrate integrated waveguide (SIW) filter are presented. The hexagonal SIW resonator which can combine flexibility of rectangular cavity and performance of circular cavity is convenient for dual-mode bandpass filters design. By introducing coupling between source and load, the filter not only has good selectivity due to two controllable transmission zeros, but also has a small size by the virtue of its single-cavity structure. A demonstration filter with a center frequency of 10 GHz and a 3 dB fractional bandwidth of 4% is designed and fabricated to validate the proposed structure. Measured results are in good agreement with simulated ones. PMID:24895669

  16. Dual-mode imaging of cutaneous tissue oxygenation and vascular function.

    PubMed

    Xu, Ronald X; Huang, Kun; Qin, Ruogu; Huang, Jiwei; Xu, Jeff S; Ding, Liya; Gnyawali, Urmila S; Gordillo, Gayle M; Gnyawali, Surya C; Sen, Chandan K

    2010-01-01

    Accurate assessment of cutaneous tissue oxygenation and vascular function is important for appropriate detection, staging, and treatment of many health disorders such as chronic wounds. We report the development of a dual-mode imaging system for non-invasive and non-contact imaging of cutaneous tissue oxygenation and vascular function. The imaging system integrated an infrared camera, a CCD camera, a liquid crystal tunable filter and a high intensity fiber light source. A Labview interface was programmed for equipment control, synchronization, image acquisition, processing, and visualization. Multispectral images captured by the CCD camera were used to reconstruct the tissue oxygenation map. Dynamic thermographic images captured by the infrared camera were used to reconstruct the vascular function map. Cutaneous tissue oxygenation and vascular function images were co-registered through fiduciary markers. The performance characteristics of the dual-mode image system were tested in humans. PMID:21178967

  17. Small Externally-fueled Heat Pipe Thermionic Reactor (SEHPTR) for dual mode applications

    NASA Astrophysics Data System (ADS)

    Malloy, John; Jacox, Michael; Zubrin, Robert

    1992-07-01

    The Small Externally Fueled Heat-Pipe Thermionic Reactor (SEHPTR) is described in the context of applications as a dual-mode nuclear power source for satellites. The SEHPTR is a thermionic power system based on a reactor with modular fuel elements around cylindrical thermionic heat-pipe modules with diodes for heat rejection. The SEHPTR concept is theorized to be suitable for directly heating hydrogen gas in the core to increase propulsion and reduce orbit-transfer times. The advantages of dual-mode operation of the SEHPTR are listed including enhanced mission safety and performance at relatively low costs. The SEHPTR could provide direct thermal thrust and an integrated stage that symbiotically utilizes electric power, direct thrust, and hydrogen arcjets. The system is argued to be more effective than a nuclear power system designed solely for electrical power production.

  18. Compact wearable dual-mode imaging system for real-time fluorescence image-guided surgery

    NASA Astrophysics Data System (ADS)

    Zhu, Nan; Huang, Chih-Yu; Mondal, Suman; Gao, Shengkui; Huang, Chongyuan; Gruev, Viktor; Achilefu, Samuel; Liang, Rongguang

    2015-09-01

    A wearable all-plastic imaging system for real-time fluorescence image-guided surgery is presented. The compact size of the system is especially suitable for applications in the operating room. The system consists of a dual-mode imaging system, see-through goggle, autofocusing, and auto-contrast tuning modules. The paper will discuss the system design and demonstrate the system performance.

  19. Compact wearable dual-mode imaging system for real-time fluorescence image-guided surgery.

    PubMed

    Zhu, Nan; Huang, Chih-Yu; Mondal, Suman; Gao, Shengkui; Huang, Chongyuan; Gruev, Viktor; Achilefu, Samuel; Liang, Rongguang

    2015-09-01

    A wearable all-plastic imaging system for real-time fluorescence image-guided surgery is presented. The compact size of the system is especially suitable for applications in the operating room. The system consists of a dual-mode imaging system, see-through goggle, autofocusing, and auto-contrast tuning modules. The paper will discuss the system design and demonstrate the system performance. PMID:26358823

  20. Numerical Investigation of Dual-Mode Scramjet Combustor with Large Upstream Interaction

    NASA Technical Reports Server (NTRS)

    Mohieldin, T. O.; Tiwari, S. N.; Reubush, David E. (Technical Monitor)

    2004-01-01

    Dual-mode scramjet combustor configuration with significant upstream interaction is investigated numerically, The possibility of scaling the domain to accelerate the convergence and reduce the computational time is explored. The supersonic combustor configuration was selected to provide an understanding of key features of upstream interaction and to identify physical and numerical issues relating to modeling of dual-mode configurations. The numerical analysis was performed with vitiated air at freestream Math number of 2.5 using hydrogen as the sonic injectant. Results are presented for two-dimensional models and a three-dimensional jet-to-jet symmetric geometry. Comparisons are made with experimental results. Two-dimensional and three-dimensional results show substantial oblique shock train reaching upstream of the fuel injectors. Flow characteristics slow numerical convergence, while the upstream interaction slowly increases with further iterations. As the flow field develops, the symmetric assumption breaks down. A large separation zone develops and extends further upstream of the step. This asymmetric flow structure is not seen in the experimental data. Results obtained using a sub-scale domain (both two-dimensional and three-dimensional) qualitatively recover the flow physics obtained from full-scale simulations. All results show that numerical modeling using a scaled geometry provides good agreement with full-scale numerical results and experimental results for this configuration. This study supports the argument that numerical scaling is useful in simulating dual-mode scramjet combustor flowfields and could provide an excellent convergence acceleration technique for dual-mode simulations.

  1. Dual-mode plasmonic nanorod type antenna based on the concept of a trapped dipole.

    PubMed

    Panaretos, Anastasios H; Werner, Douglas H

    2015-04-01

    In this paper we theoretically investigate the feasibility of creating a dual-mode plasmonic nanorod antenna. The proposed design methodology relies on adapting to optical wavelengths the principles of operation of trapped dipole antennas, which have been widely used in the low MHz frequency range. This type of antenna typically employs parallel LC circuits, also referred to as "traps", which are connected along the two arms of the dipole. By judiciously choosing the resonant frequency of these traps, as well as their position along the arms of the dipole, it is feasible to excite the λ/2 resonance of both the original dipole as well as the shorter section defined by the length of wire between the two traps. This effectively enables the dipole antenna to have a dual-mode of operation. Our analysis reveals that the implementation of this concept at the nanoscale requires that two cylindrical pockets (i.e. loading volumes) be introduced along the length of the nanoantenna, inside which plasmonic core-shell particles are embedded. By properly selecting the geometry and constitution of the core-shell particle as well as the constitution of the host material of the two loading volumes and their position along the nanorod, the equivalent effect of a resonant parallel LC circuit can be realized. This effectively enables a dual-mode operation of the nanorod antenna. The proposed methodology introduces a compact approach for the realization of dual-mode optical sensors while at the same time it clearly illustrates the inherent tuning capabilities that core-shell particles can offer in a practical framework. PMID:25968668

  2. Dual-mode microwave system to enhance early detection of cancer

    NASA Technical Reports Server (NTRS)

    Carr, K. L.; El-Mahdi, A. M.; Shaeffer, J.

    1981-01-01

    A dual-mode microwave system has been developed that will permit early detection of cancer. The system combines the use of the passive microwave radiometer with an active transmitter. The active transmitter will provide localized heating to enhance early detection by taking advantage of the differential heating (i.e., tumor temperature with respect to surrounding tissue) associated with the thermal characteristics of tumors.

  3. Theoretical modeling of a self-referenced dual mode SPR sensor utilizing indium tin oxide film

    NASA Astrophysics Data System (ADS)

    Srivastava, Sachin K.; Verma, Roli; Gupta, Banshi D.

    2016-06-01

    A prism based dual mode SPR sensor was theoretically modeled to work as a self-referenced sensor in spectral interrogation scheme. Self-referenced sensing was achieved by sandwiching an indium tin oxide thin film in between the prism base and the metal layer. The proposed sensor possesses two plasmon modes similar to long and short range SPRs (LR- and SR-SPRs) and we have analogically used LRSPR and SRSPR for them. However, these modes do not possess usual long range character due to the losses introduced by the imaginary part of indium tin oxide (ITO) dielectric function. One of the two plasmon modes responds to change in analyte refractive index while the other remains fixed. The influence of various design parameters on the performance of the sensor was evaluated. The performance of the proposed sensor was compared, via control simulations, with established dual mode geometries utilizing silicon dioxide (SiO2), Teflon AF-1600 and Cytop. The design parameters of the established geometries were optimized to obtain self-referenced sensing operation. Trade-offs between the resonance spectral width, minimum reflectivity, shift in resonance wavelength and angle of incidence were examined for optimal design. The present study will be useful in the fabrication of self-referenced sensors where the ambient conditions are not quite stable.

  4. A digitally controlled PWM/PSM dual-mode DC/DC converter

    NASA Astrophysics Data System (ADS)

    Shaowei, Zhen; Bo, Zhang; Ping, Luo; Sijian, Hou; Jingxin, Ye; Xiao, Ma

    2011-11-01

    A digitally controlled pulse width modulation/pulse skip modulation (PWM/PSM) dual-mode buck DC/DC converter is proposed. Its operation mode can be automatically chosen as continuous conduction mode (CCM) or discontinuous conduction mode (DCM). The converter works in PSM at DCM and in 2 MHz PWM at CCM. Switching loss is reduced at a light load by skipping cycles. Thus high conversion efficiency is realized in a wide load current. The implementations of PWM control blocks, such as the ADC, the digital pulse width modulator (DPWM) and the loop compensator, and PSM control blocks are described in detail. The parameters of the loop compensator can be programmed for different external component values and switching frequencies, which is much more flexible than its analog rivals. The chip is manufactured in 0.13 μm CMOS technology and the chip area is 1.21 mm2. Experimental results show that the conversion efficiency is high, being 90% at 200 mA and 67% at 20 mA. Meanwhile, the measured load step response shows that the proposed dual-mode converter has good stability.

  5. Dual-Pump CARS Measurements in the University of Virginia's Dual-Mode Scramjet: Configuration "A"

    NASA Technical Reports Server (NTRS)

    Cutler, Andrew D.; Magnotti, Gaetano; Gallo, Emanuela; Danehy, Paul M.; Rockwell, Robert; Goyne, Christopher P.; McDaniel, James

    2012-01-01

    In this paper we describe efforts to obtain canonical data sets to assist computational modelers in their development of models for the prediction of mixing and combustion in scramjet combustors operating in the ramjet-scramjet transition regime. The CARS technique is employed to acquire temporally and spatially resolved measurements of temperature and species mole-fraction at four planes, one upstream of an H2 fuel injector and three downstream. The technique is described and results are presented for cases with and without chemical reaction. The vibrational energy mode in the heated airstream of the combustor was observed to be frozen at near facility heater conditions and significant nonuniformities in temperature were observed, attributed to nonuniformities of temperature exiting the heater. The measurements downstream of fuel injection show development of mixing and combustion, and are already proving useful to the modelers.

  6. Interstitial thermal ablation with a fast rotating dual-mode transducer.

    PubMed

    Bouchoux, Guillaume; Owen, Neil; Chavrier, Francoise; Berriet, Rémi; Fleury, Gérard; Chapelon, Jean-Yves; Lafon, Cyril

    2010-05-01

    Interstitial ultrasound applicators can be a minimally invasive alternative for treating targets that are unresectable or are inaccessible by extracorporeal methods. Dual-mode transducers for ultrasound imaging and therapy were developed to address the constraints of a miniaturized applicator and real-time treatment monitoring. We propose an original treatment strategy that combines ultrasound imaging and therapy using a dual-mode transducer rotating at 8 revolutions per second. Real-time B-mode imaging was interrupted to emit high-intensity ultrasound over a selected therapy aperture. A full 360 degrees image was taken every 8th rotation to image the therapy aperture. Numerical simulations were performed to study the effect of rotation on tissue heating, and to study the effect of the treatment sequence on transducer temperature. With the time-averaged transducer surface intensity held at 12 W/cm(2) to maintain transducer temperature below 66 degrees C, higher field intensities and deeper lesions were produced by narrower therapy apertures. A prototype system was built and tested using in vitro samples of porcine liver. Lesions up to 8 mm were produced using a time-averaged transducer surface intensity of 12 W/cm(2) applied for a period of 240 s over a therapy aperture of 40 degrees. Apparent strain imaging of the therapy aperture improved the contrast between treated and spared tissues, which could not be differentiated on B-mode images. With appropriate limits on the transducer output, real-time imaging and deep thermal ablation are feasible and sustainable using a rotating dual-mode transducer. PMID:20442018

  7. Mini-cavity plasma core reactors for dual-mode space nuclear power/propulsion systems. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Chow, S.

    1976-01-01

    A mini-cavity plasma core reactor is investigated for potential use in a dual-mode space power and propulsion system. In the propulsive mode, hydrogen propellant is injected radially inward through the reactor solid regions and into the cavity. The propellant is heated by both solid driver fuel elements surrounding the cavity and uranium plasma before it is exhausted out the nozzle. The propellant only removes a fraction of the driver power, the remainder is transferred by a coolant fluid to a power conversion system, which incorporates a radiator for heat rejection. Neutronic feasibility of dual mode operation and smaller reactor sizes than those previously investigated are shown to be possible. A heat transfer analysis of one such reactor shows that the dual-mode concept is applicable when power generation mode thermal power levels are within the same order of magnitude as direct thrust mode thermal power levels.

  8. Dual chamber pacing: how many patients remain in DDD mode over the long term?

    PubMed Central

    Ibrahim, B.; Sanderson, J. E.; Wright, B.; Palmer, R.

    1995-01-01

    OBJECTIVE--DDD pacing is better than VVI pacing in complete heart block and sick sinus syndrome but is more expensive and demanding. In addition, some patients have to be programmed out of DDD mode and this may have an important impact on the cost-effectiveness of DDD pacing. The purpose of this study was to determine how many patients remain in DDD mode over the long term (up to 10 years). DESIGN--A retrospective analysis of the outcome over 10 years of consecutive patients who had their pacemakers programmed initially in DDD mode. SETTING--A district general hospital. PATIENTS--249 patients with DDD pacemakers. Sixty two patients (24.9%) had predominantly sick sinus syndrome and 180 (72.3%) had predominantly atrioventricular conduction disease. Mean (range) complete follow up for this group of patients was 32 months (1-10 years). RESULTS--Cumulative survival of DDD mode was 83.5% at 60 months. Atrial fibrillation was the commonest reason for abandonment of DDD pacing. Atrial fibrillation developed in 30 patients (12%), with atrial flutter in three (1.2%). Loss of atrial sensing or pacing, pacemaker mediated tachycardia, and various other reasons accounted for reprogramming out of DDD mode in eight patients (3.2%). Overall, an atrial pacing mode was maintained in 91% and VVI pacing was needed in only 9%. CONCLUSIONS--With careful use of programming facilities and appropriate secondary intervention, most patients with dual chamber pacemakers can be maintained successfully in DDD or an alternative atrial pacing mode until elective replacement, although atrial arrhythmia remains a significant problem. There are no good reasons, other than cost, for not using dual chamber pacing routinely as suggested by recent guidelines and this policy can be achieved successfully in a district general hospital pacing centre. PMID:7662461

  9. A dual mode imaging array for damage detection in grout structures

    NASA Astrophysics Data System (ADS)

    Tian, Zhenhua; Yu, Lingyu; EL-Batanouny, Mohamed; Ziehl, Paul; Zhao, Liuxian

    2013-04-01

    Due to the heterogeneous nature of the cement-based materials, the ultrasonic waves in concrete exhibit highly scattering and attenuation, leading to the difficulty of concrete damaged detection. This paper presents a dual mode ultrasonic array imaging methodology that can map damage using Rayleigh surface waves and permanently installed piezoelectric sensors. The dual mode sensing integrates passive acoustic emission and active ultrasonic wave inspection. When a crack is developing, acoustic emission (AE) occurs and the disturbance can propagate outwards along the structure surface. A novel AE source imaging algorithm has been developed to detect and locate the AE source. Once the AE source is located, the sensor array switches to its active mode. For active sensing, one sensor in the array is used to generate Rayleigh wave for interrogation, while all the others are used as the wave receivers. All the sensory data are processed by the active ultrasonic array imaging algorithm. The proof-of-concept testing was performed on a grout specimen with representative dimensions. The passive array imaging algorithm was able to locate the AE source simulated by pencil lead break while active sensing imaging was able to detect the damage simulated by a hole. The duel mode imaging method is promising and economically beneficial for solving a key source localization problem in damage detection on large concrete structures.

  10. Multiplexed Millimeter Wave Communication with Dual Orbital Angular Momentum (OAM) Mode Antennas

    PubMed Central

    Hui, Xiaonan; Zheng, Shilie; Chen, Yiling; Hu, Yiping; Jin, Xiaofeng; Chi, Hao; Zhang, Xianmin

    2015-01-01

    Communications using the orbital angular momentum (OAM) of radio waves have attracted much attention in recent years. In this paper, a novel millimeter-wave dual OAM mode antenna is cleverly designed, using which a 60 GHz wireless communication link with two separate OAM channels is experimentally demonstrated. The main body of the dual OAM antenna is a traveling-wave ring resonator using two feeding ports fed by a 90° hybrid coupler. A parabolic reflector is used to focus the beams. All the antenna components are fabricated by 3D printing technique and the electro-less copper plating surface treatment process. The performances of the antenna, such as S-parameters, near-fields, directivity, and isolation between the two OAM modes are measured. Experimental results show that this antenna can radiate two coaxially propagating OAM modes beams simultaneously. The multiplexing and de-multiplexing are easily realized in the antennas themselves. The two OAM mode channels have good isolation of more than 20 dB, thus ensuring the reliable transmission links at the same time. PMID:25988501

  11. Multiplexed Millimeter Wave Communication with Dual Orbital Angular Momentum (OAM) Mode Antennas

    NASA Astrophysics Data System (ADS)

    Hui, Xiaonan; Zheng, Shilie; Chen, Yiling; Hu, Yiping; Jin, Xiaofeng; Chi, Hao; Zhang, Xianmin

    2015-05-01

    Communications using the orbital angular momentum (OAM) of radio waves have attracted much attention in recent years. In this paper, a novel millimeter-wave dual OAM mode antenna is cleverly designed, using which a 60 GHz wireless communication link with two separate OAM channels is experimentally demonstrated. The main body of the dual OAM antenna is a traveling-wave ring resonator using two feeding ports fed by a 90° hybrid coupler. A parabolic reflector is used to focus the beams. All the antenna components are fabricated by 3D printing technique and the electro-less copper plating surface treatment process. The performances of the antenna, such as S-parameters, near-fields, directivity, and isolation between the two OAM modes are measured. Experimental results show that this antenna can radiate two coaxially propagating OAM modes beams simultaneously. The multiplexing and de-multiplexing are easily realized in the antennas themselves. The two OAM mode channels have good isolation of more than 20 dB, thus ensuring the reliable transmission links at the same time.

  12. Dipeptidyl Enoates As Potent Rhodesain Inhibitors That Display a Dual Mode of Action.

    PubMed

    Royo, Santiago; Rodríguez, Santiago; Schirmeister, Tanja; Kesselring, Jochen; Kaiser, Marcel; González, Florenci V

    2015-09-01

    Dipeptidyl enoates were prepared through a high-yielding two-step synthetic route. They have a dipeptidic structure with a 4-oxoenoate moiety as a warhead with multiple reactive sites. Dipeptidyl enoates were screened against rhodesain and human cathepsins B and L, and were found to be potent and selective inhibitors of rhodesain. Among them (S,E)-ethyl 5-((S)-2-{[(benzyloxy)carbonyl]amino}-3-phenylpropanamido)-7-methyl-4-oxooct-2-enoate (6) was the most potent, with an IC50 value of 16.4 nM and kinact /Ki =1.6×10(6)  M(-1)  s(-1) against rhodesain. These dipeptidyl enoates display a reversible mode of inhibition at very low concentrations and an irreversible mode at higher concentrations. Inhibition kinetics data, supported by docking studies, suggest a dual mode of action via attack of cysteine thiolate at two reactive positions. PMID:26179752

  13. Stable single-longitudinal-mode erbium-doped fiber laser with dual-ring structure

    NASA Astrophysics Data System (ADS)

    Yeh, Chien-Hung; Chen, Jhih-Yu; Chen, Hone-Zhang; Chow, Chi-Wai

    2016-01-01

    In this paper, we propose and demonstrate experimentally a stable erbium-doped fiber (EDF) laser with single-longitudinal-mode (SLM) output by employing dual-ring structure. By using the multiple ring architecture, the densely spaced longitudinal modes would be suppressed and generated a SLM lasing output. In the measurement, the wavelength can be tuned in the wavelengths of 1530.0-1560.0 nm. And the measured output powers and side-mode suppression ratios (SMSRs) are between 5.2 and 14.1 dBm and 30.4 and 39.8 dB, respectively. In addition, the output stabilities of wavelength and power in proposed fiber laser have also been discussed.

  14. A 20 GHz, high efficiency dual mode TWT for the ACTS program. [Advanced Communications Technology Satellite

    NASA Technical Reports Server (NTRS)

    Muennemann, Frank; Dombro, Louis; Long, Jin

    1986-01-01

    The development of a 50 W/10 W dual mode K-band downlink TWT is examined, and its performance is evaluated. The designs of the electron gun, RF circuit, and collector for the TWT, which is enclosed in a capsule, are described. It is observed that the high power mode (HPM) power output is at 50 GHz and the low power mode (LPM) output is at 12 GHz; the saturated gain is 52.5 dB for HPM and 3 dB for LPM; the AM-PM is 4.2 dB; the HPM dc power output is 104 W; and the LPM dc output is 42 W; and the efficiency is 45 percent for the HPM and 28.6 percent for the LPM.

  15. A novel buck/LDO dual-mode DC—DC converter for efficiency improvement

    NASA Astrophysics Data System (ADS)

    Shiquan, Fan; Zhongming, Xue; Hao, Lu; Hui, Zhao; Li, Geng

    2013-10-01

    A novel buck/LDO dual-mode (BLDM) converter using a multiplexing power MOS transistor is proposed, which adaptively switches between buck mode and LDO mode to improve conversion efficiency. The chip was fabricated in a standard 0.35 μm CMOS process. Measurement results show that the peak efficiency is 97%. For the light load operation, the efficiency is improved by 14%. The efficiency keeps higher than 82.5% for the load current of 50 mA without any complex control or extra EMI due to the normal method of pulse frequency modulation (PFM) control used for improving the light load efficiency. It does not cost much extra chip area because no additional regulator PMOS is needed. It is more suitable for noise-restricted systems and battery-powered electronic devices for when battery voltage drops because of long hours of work.

  16. Quasinormal modes of self-dual warped AdS3 black hole in topological massive gravity

    NASA Astrophysics Data System (ADS)

    Li, Ran; Ren, Ji-Rong

    2011-03-01

    We consider the scalar, vector and spinor field perturbations in the background of self-dual warped AdS3 black hole of topological massive gravity. The corresponding exact expressions for quasinormal modes are obtained by analytically solving the perturbation equations and imposing the vanishing Dirichlet boundary condition at asymptotic infinity. It is expected that the quasinormal modes agree with the poles of retarded Green’s functions of the CFT dual to self-dual warped AdS3 black hole. Our results provide a quantitative test of the warped AdS/CFT correspondence.

  17. A dual mode charge pump with adaptive output used in a class G audio power amplifier

    NASA Astrophysics Data System (ADS)

    Yong, Feng; Zhenfei, Peng; Shanshan, Yang; Zhiliang, Hong; Yang, Liu

    2011-04-01

    A dual mode charge pump to produce an adaptive power supply for a class G audio power amplifier is presented. According to the amplitude of the input signals, the charge pump has two level output voltage rails available to save power. It operates both in current mode at high output load and in pulse frequency modulation (PFM) at light load to reduce the power dissipation. Also, dynamic adjustment of the power stage transistor size based on load current at the PFM mode is introduced to reduce the output voltage ripple and prevent the switching frequency from audio range. The prototype is implemented in 0.18 μm 3.3 V CMOS technology. Experimental results show that the maximum power efficiency of the charge pump is 79.5% @ 0.5x mode and 83.6% @ 1x mode. The output voltage ripple is less than 15 mV while providing 120 mA of the load current at PFM control and less than 18 mV while providing 300 mA of the load current at current mode control. An analytical model for ripple voltage and efficiency calculation of the proposed PFM control demonstrates reasonable agreement with measured results.

  18. Spectrally interleaved, comb-mode-resolved spectroscopy using swept dual terahertz combs

    PubMed Central

    Hsieh, Yi-Da; Iyonaga, Yuki; Sakaguchi, Yoshiyuki; Yokoyama, Shuko; Inaba, Hajime; Minoshima, Kaoru; Hindle, Francis; Araki, Tsutomu; Yasui, Takeshi

    2014-01-01

    Optical frequency combs are innovative tools for broadband spectroscopy because a series of comb modes can serve as frequency markers that are traceable to a microwave frequency standard. However, a mode distribution that is too discrete limits the spectral sampling interval to the mode frequency spacing even though individual mode linewidth is sufficiently narrow. Here, using a combination of a spectral interleaving and dual-comb spectroscopy in the terahertz (THz) region, we achieved a spectral sampling interval equal to the mode linewidth rather than the mode spacing. The spectrally interleaved THz comb was realized by sweeping the laser repetition frequency and interleaving additional frequency marks. In low-pressure gas spectroscopy, we achieved an improved spectral sampling density of 2.5 MHz and enhanced spectral accuracy of 8.39 × 10−7 in the THz region. The proposed method is a powerful tool for simultaneously achieving high resolution, high accuracy, and broad spectral coverage in THz spectroscopy. PMID:24448604

  19. 60-GHz Millimeter-wave Over Fiber with Directly Modulated Dual-mode Laser Diode.

    PubMed

    Tsai, Cheng-Ting; Lin, Chi-Hsiang; Lin, Chun-Ting; Chi, Yu-Chieh; Lin, Gong-Ru

    2016-01-01

    A directly modulated dual-mode laser diode (DMLD) with third-order intermodulation distortion (IMD3) suppression is proposed for a 60-GHz millimeter-wave over fiber (MMWoF) architecture, enabling new fiber-wireless communication access to cover 4-km single-mode-fiber (SMF) and 3-m wireless 16-QAM OFDM transmissions. By dual-mode injection-locking, the throughput degradation of the DMLD is mitigated with saturation effect to reduce its threshold, IMD3 power and relative intensity noise to 7.7 mA, -85 dBm and -110.4 dBc/Hz, respectively, providing huge spurious-free dynamic range of 85.8 dB/Hz(2/3). This operation suppresses the noise floor of the DMLD carried QPSK-OFDM spectrum by 5 dB. The optical receiving power is optimized to restrict the power fading effect for improving the bit error rate to 1.9 × 10(-3 )and the receiving power penalty to 1.1 dB. Such DMLD based hybrid architecture for 60-GHz MMW fiber-wireless access can directly cover the current optical and wireless networks for next-generation indoor and short-reach mobile communications. PMID:27297267

  20. Dual-mode operation of 2D material-base hot electron transistors

    PubMed Central

    Lan, Yann-Wen; Torres, Jr., Carlos M.; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R.; Lerner, Mitchell B.; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L.

    2016-01-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications. PMID:27581550

  1. 60-GHz Millimeter-wave Over Fiber with Directly Modulated Dual-mode Laser Diode

    PubMed Central

    Tsai, Cheng-Ting; Lin, Chi-Hsiang; Lin, Chun-Ting; Chi, Yu-Chieh; Lin, Gong-Ru

    2016-01-01

    A directly modulated dual-mode laser diode (DMLD) with third-order intermodulation distortion (IMD3) suppression is proposed for a 60-GHz millimeter-wave over fiber (MMWoF) architecture, enabling new fiber-wireless communication access to cover 4-km single-mode-fiber (SMF) and 3-m wireless 16-QAM OFDM transmissions. By dual-mode injection-locking, the throughput degradation of the DMLD is mitigated with saturation effect to reduce its threshold, IMD3 power and relative intensity noise to 7.7 mA, −85 dBm and −110.4 dBc/Hz, respectively, providing huge spurious-free dynamic range of 85.8 dB/Hz2/3. This operation suppresses the noise floor of the DMLD carried QPSK-OFDM spectrum by 5 dB. The optical receiving power is optimized to restrict the power fading effect for improving the bit error rate to 1.9 × 10−3 and the receiving power penalty to 1.1 dB. Such DMLD based hybrid architecture for 60-GHz MMW fiber-wireless access can directly cover the current optical and wireless networks for next-generation indoor and short-reach mobile communications. PMID:27297267

  2. 60-GHz Millimeter-wave Over Fiber with Directly Modulated Dual-mode Laser Diode

    NASA Astrophysics Data System (ADS)

    Tsai, Cheng-Ting; Lin, Chi-Hsiang; Lin, Chun-Ting; Chi, Yu-Chieh; Lin, Gong-Ru

    2016-06-01

    A directly modulated dual-mode laser diode (DMLD) with third-order intermodulation distortion (IMD3) suppression is proposed for a 60-GHz millimeter-wave over fiber (MMWoF) architecture, enabling new fiber-wireless communication access to cover 4-km single-mode-fiber (SMF) and 3-m wireless 16-QAM OFDM transmissions. By dual-mode injection-locking, the throughput degradation of the DMLD is mitigated with saturation effect to reduce its threshold, IMD3 power and relative intensity noise to 7.7 mA, ‑85 dBm and ‑110.4 dBc/Hz, respectively, providing huge spurious-free dynamic range of 85.8 dB/Hz2/3. This operation suppresses the noise floor of the DMLD carried QPSK-OFDM spectrum by 5 dB. The optical receiving power is optimized to restrict the power fading effect for improving the bit error rate to 1.9 × 10‑3 and the receiving power penalty to 1.1 dB. Such DMLD based hybrid architecture for 60-GHz MMW fiber-wireless access can directly cover the current optical and wireless networks for next-generation indoor and short-reach mobile communications.

  3. Dual-mode operation of 2D material-base hot electron transistors.

    PubMed

    Lan, Yann-Wen; Torres, Carlos M; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R; Lerner, Mitchell B; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L

    2016-01-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications. PMID:27581550

  4. Novel dual-mode immunomagnetic method for studying reactivation of nerve agent-inhibited butyrylcholinesterase.

    PubMed

    Abney, Carter W; Knaack, Jennifer L S; Ali, Ahmed A I; Johnson, Rudolph C

    2013-05-20

    A novel immunomagnetic method has been developed for the simultaneous measurement of organophosphorus nerve agent (OPNA) adducts to butyrylcholinesterase (BuChE) and free OPNAs in serum. This new approach, deemed dual-mode immunomagnetic analysis (Dual-Mode IMA), combines immunomagnetic separation (IMS) and immunomagnetic scavenging (IMSc) and has been used to measure the effectiveness of cholinesterase reactivators on OPNA-inhibited BuChE in serum. BuChE inhibited by the nerve agent VX, uninhibited BuChE, and unbound VX were measured up to 1 h after the addition of oxime reactivators pralidoxime (2-PAM) and obidoxime. IMS experiments consisted of extracting BuChE and VX-BuChE serum adducts using antibutyrylcholinesterase monoclonal antibodies conjugated to protein-G ferromagnetic particles. In a parallel set of experiments using IMSc, BuChE-coated magnetic beads were used to extract free VX from protein-depleted serum. Adducts from both IMS and IMSc were analyzed using a published IMS liquid chromatography tandem mass spectrometry (IMS-LC-MS/MS) protocol, which has also been demonstrated with other OPNAs. By applying this Dual-Mode IMA approach, 2-PAM was observed to be more potent than obidoxime in reactivating VX-adducted BuChE. VX-BuChE peptide concentrations initially measured at 19.7 ± 0.7 ng/mL decreased over 1 h to 10.6 ± 0.6 ng/mL when reactivated with 2-PAM and 14.4 ± 1.2 ng/mL when reactivated with obidoxime. These experiments also show that previously published IMS-LC-MS/MS analyses are compatible with serum treated with oximes. Dual-Mode IMA is the first immunoaffinity method developed for the simultaneous measurement of OPNA adducted BuChE, unadducted BuChE, and free nerve agent in serum and is a promising new tool for studying reactivator effectiveness on cholinesterases inhibited by nerve agents. PMID:23656164

  5. Dual-mode self-validating resistance/Johnson noise thermometer system

    DOEpatents

    Shepard, Robert L.; Blalock, Theron V.; Roberts, Michael J.

    1993-01-01

    A dual-mode Johnson noise and DC resistance thermometer capable of use in control systems where prompt indications of temperature changes and long term accuracy are needed. A resistance-inductance-capacitance (RLC) tuned circuit produces a continuous voltage signal for Johnson noise temperature measurement. The RLC circuit provides a mean-squared noise voltage that depends only on the capacitance used and the temperature of the sensor. The sensor has four leads for simultaneous coupling to a noise signal processor and to a DC resistance signal processor.

  6. 10 kWe dual-mode space nuclear power system for military and scientific applications

    NASA Astrophysics Data System (ADS)

    Malloy, John; Westerman, Kurt; Rochow, Richard; Scoles, Stephen

    The Small Externally-fueled Heat Pipe Thermionic Reactor concept is used as the basis of a 10 kWe dual-mode space power system scheme that generates both arcjet propulsion system power and direct (hydrogen propellant-heating) thrust. This direct-thrust feature allows the nuclear-power system to move a payload from LEO to GEO in less than one month, using half as much propellant as a cryogenic-fuel chemical rocket. The nuclear reactor uses 36 thermionic heat-pipe modules, which produce electricity within the reactor and remove waste heat.

  7. Dual-mode spectral imaging system employing a focus variable lens

    NASA Astrophysics Data System (ADS)

    Förster, Erik; Stürmer, Moritz; Wallrabe, Ulrike; Korvink, Jan; Bohnert, Patrick; Brunner, Robert

    2016-04-01

    This paper presents a dual-mode spectral imaging system, which allows switching between pure lateral imaging and the spectrally resolved recording of spatial information. The optical system was equipped with tunable functionalities in order to achieve high flexibility, cover a wide range of object distances, and address extended field angles. A fluidic membrane lens was used for the variable focus, and the recording of the laterally extended scene was made possible by successively adjusting the different tilting angles to the different object positions. The capability and performance of the spectral imaging system were assessed using various test scenes, with different aimed field positions and changing object distances.

  8. Dual-Mode Combustion of Hydrogen in a Mach 5, Continuous-Flow Facility

    NASA Technical Reports Server (NTRS)

    Goyne, C. P.; McDaniel, J. C.; Quagliaroli, T. M.; Krauss, R. H.; Day, S. W.; Reubush, D. E. (Technical Monitor); McClinton, C. R. (Technical Monitor); Reubush, D. E.

    2001-01-01

    Results of an experimental and numerical study of a dual-mode scramjet combustor are reported. The experiment consisted of a direct-connect test of a Mach 2 hydrogen-air combustor with a single unswept-ramp fuel injector. The flow stagnation enthalpy simulated a flight Mach number of 5. Measurements were obtained using conventional wall instrumentation and a particle-imaging laser diagnostic technique. The particle imaging was enabled through the development of a new apparatus for seeding fine silicon dioxide particles into the combustor fuel stream. Numerical simulations of the combustor were performed using the GASP code. The modeling, and much of the experimental work, focused on the supersonic combustion mode. Reasonable agreement was observed between experimental and numerical wall pressure distributions. However, the numerical model was unable to predict accurately the effects of combustion on the fuel plume size, penetration, shape, and axial growth.

  9. Isolator-combustor interaction in a dual-mode scramjet engine

    NASA Technical Reports Server (NTRS)

    Pratt, David T.; Heiser, William H.

    1993-01-01

    A constant-area diffuser, or 'isolator', is required in both the ramjet and scramjet operating regimes of a dual-mode engine configuration in order to prevent unstarts due to pressure feedback from the combustor. Because the nature of the combustor-isolator interaction is different in the two operational modes, however, attention is presently given to the use of thermal vs kinetic energy coordinates for these interaction processes' visualization. The results of the analysis thus conducted indicate that the isolator requires severe flow separation at combustor entry, and that its entropy-generating characteristics are more severe than an equivalent oblique shock. A constant-area diffuser is only marginally able to contain the equivalent normal shock required for subsonic combustor entry.

  10. Wideband Fully-Programmable Dual-Mode CMOS Analogue Front-End for Electrical Impedance Spectroscopy.

    PubMed

    Valente, Virgilio; Demosthenous, Andreas

    2016-01-01

    This paper presents a multi-channel dual-mode CMOS analogue front-end (AFE) for electrochemical and bioimpedance analysis. Current-mode and voltage-mode readouts, integrated on the same chip, can provide an adaptable platform to correlate single-cell biosensor studies with large-scale tissue or organ analysis for real-time cancer detection, imaging and characterization. The chip, implemented in a 180-nm CMOS technology, combines two current-readout (CR) channels and four voltage-readout (VR) channels suitable for both bipolar and tetrapolar electrical impedance spectroscopy (EIS) analysis. Each VR channel occupies an area of 0.48 mm 2 , is capable of an operational bandwidth of 8 MHz and a linear gain in the range between -6 dB and 42 dB. The gain of the CR channel can be set to 10 kΩ, 50 kΩ or 100 kΩ and is capable of 80-dB dynamic range, with a very linear response for input currents between 10 nA and 100 μ A. Each CR channel occupies an area of 0.21 mm 2 . The chip consumes between 530 μ A and 690 μ A per channel and operates from a 1.8-V supply. The chip was used to measure the impedance of capacitive interdigitated electrodes in saline solution. Measurements show close matching with results obtained using a commercial impedance analyser. The chip will be part of a fully flexible and configurable fully-integrated dual-mode EIS system for impedance sensors and bioimpedance analysis. PMID:27463721

  11. Review of the Development and Testing of a New Family of Boron and Gadolinium-Bearing Dual Thermal Neutron Absorbing Alloys - 13026

    SciTech Connect

    Schmidt, M.L.; Del Corso, G.J.; Klankowski, K.A.; Lherbier, L.W.; Novotnak, D.J.

    2013-07-01

    The development of a new class of Fe-based thermal neutron absorbing alloys (patent pending) containing both natural boron (B) and gadolinium (Gd) is reviewed. Testing has shown that Ar and N inert gas atomized powder metallurgy (PM) variants offer superior processability coupled with improved mechanical properties that exhibit reduced anisotropy and reduced corrosion rates compared to conventional cast/wrought processed material. PM processing results in a microstructure containing a uniform distribution of second phase borides and gadolinides, and the morphology of the gadolinides prevents the formation low melting point Gd-bearing phases at solidifying austenite boundaries. The new T316-based materials containing both B and Gd exhibit superior corrosion resistance compared to straight B-bearing T304 materials. By keeping the B content < 1 weight percent (%) and using Gd to attain an equivalent B (B{sub Eq}) content higher than that achievable through the use of B only, the new materials exhibit superior ductility, toughness and bendability as a result of significantly reduced area fraction of Cr-rich M{sub 2}B borides. Limiting the total area fraction of second phase particles to < 22% insures a product with superior bendability. By restricting B to < 1% and using Gd up to 2.5%, B{sub Eq} levels approaching 12% can be attained that provide a cost effective improvement in thermal neutron absorption capability compared to using B-10 enriched boron. The new materials can be easily bent during fabrication compared to existing metal matrix composite materials while offering similar thermal neutron absorption capability. Production lots containing B{sub Eq} levels of 4.0 and 7.5% (Micro-Melt{sup R} DuoSorb{sup TM} 316NU-40 and 75, respectively) are in the process of being fabricated for customer trial material. (authors)

  12. Photoacoustic-guided ultrasound therapy with a dual-mode ultrasound array

    NASA Astrophysics Data System (ADS)

    Prost, Amaury; Funke, Arik; Tanter, Mickaël; Aubry, Jean-François; Bossy, Emmanuel

    2012-06-01

    Photoacoustics has recently been proposed as a potential method to guide and/or monitor therapy based on high-intensity focused ultrasound (HIFU). We experimentally demonstrate the creation of a HIFU lesion at the location of an optical absorber, by use of photoacoustic signals emitted by the absorber detected on a dual mode transducer array. To do so, a dedicated ultrasound array intended to both detect photoacoustic waves and emit HIFU with the same elements was used. Such a dual-mode array provides automatically coregistered reference frames for photoacoustic detection and HIFU emission, a highly desired feature for methods involving guidance or monitoring of HIFU by use of photoacoustics. The prototype is first characterized in terms of both photoacoustic and HIFU performances. The probe is then used to perform an idealized scenario of photoacoustic-guided therapy, where photoacoustic signals generated by an absorbing thread embedded in a piece of chicken breast are used to automatically refocus a HIFU beam with a time-reversal mirror and necrose the tissue at the location of the absorber.

  13. Three-Dimensional Effects in Modeling of Dual-Mode Scramjets

    NASA Technical Reports Server (NTRS)

    Rodriguez, C. G.; White, J. A.; Riggins, D. W.

    2000-01-01

    A numerical investigation of an experimental dual-mode scramjet configuration is performed. Both experimental and numerical results indicate significant upstream interaction for this case. Several computational cases are examined: these include the use of jet-to-jet symmetry and entire half-duct modeling. Grid convergence, turbulence modeling, and wall temperature effects are studied in terms of wall pressure predictions and flow-field characteristics. Wall pressure comparisons between CFD and experiment show fair agreement for the jet-to-jet case. However, further computations of the entire half-duct show the development of a large sidewall separation zone extending much further upstream than the separation zone at the duct centerline. This sidewall separation is the dominant feature in the CFD-generated flowfield but is not evident in the experimental data, resulting in a unfavorable comparison between CFD and experimental data. Current work aimed at resolving this issue and at further understanding asymmetric flow-structures in dual-mode flow-fields is discussed.

  14. The design of dual-mode complex signal processors based on quadratic modular number codes

    NASA Astrophysics Data System (ADS)

    Jenkins, W. K.; Krogmeier, J. V.

    1987-04-01

    It has been known for a long time that quadratic modular number codes admit an unusual representation of complex numbers which leads to complete decoupling of the real and imaginary channels, thereby simplifying complex multiplication and providing error isolation between the real and imaginary channels. This paper first presents a tutorial review of the theory behind the different types of complex modular rings (fields) that result from particular parameter selections, and then presents a theory for a 'dual-mode' complex signal processor based on the choice of augmented power-of-2 moduli. It is shown how a diminished-1 binary code, used by previous designers for the realization of Fermat number transforms, also leads to efficient realizations for dual-mode complex arithmetic for certain augmented power-of-2 moduli. Then a design is presented for a recursive complex filter based on a ROM/ACCUMULATOR architecture and realized in an augmented power-of-2 quadratic code, and a computer-generated example of a complex recursive filter is shown to illustrate the principles of the theory.

  15. Photoacoustic-guided ultrasound therapy with a dual-mode ultrasound array.

    PubMed

    Prost, Amaury; Funke, Arik; Tanter, Mickaël; Aubry, Jean-François; Bossy, Emmanuel

    2012-06-01

    Photoacoustics has recently been proposed as a potential method to guide and/or monitor therapy based on high-intensity focused ultrasound (HIFU). We experimentally demonstrate the creation of a HIFU lesion at the location of an optical absorber, by use of photoacoustic signals emitted by the absorber detected on a dual mode transducer array. To do so, a dedicated ultrasound array intended to both detect photoacoustic waves and emit HIFU with the same elements was used. Such a dual-mode array provides automatically coregistered reference frames for photoacoustic detection and HIFU emission, a highly desired feature for methods involving guidance or monitoring of HIFU by use of photoacoustics. The prototype is first characterized in terms of both photoacoustic and HIFU performances. The probe is then used to perform an idealized scenario of photoacoustic-guided therapy, where photoacoustic signals generated by an absorbing thread embedded in a piece of chicken breast are used to automatically refocus a HIFU beam with a time-reversal mirror and necrose the tissue at the location of the absorber. PMID:22734735

  16. Use of a compact range approach to evaluate rf and dual-mode missiles

    NASA Astrophysics Data System (ADS)

    Willis, Kenneth E.; Weiss, Yosef

    2000-07-01

    This paper describes a hardware-in-the-loop (HWIL) system developed for testing Radio Frequency (RF), Infra-Red (IR), and Dual-Mode missile seekers. The system consists of a unique hydraulic five-axis (three seeker axes plus two target axes) Flight Motion Table (FMT), an off-axis parabolic reflector, and electronics required to generate the signals to the RF feeds. RF energy that simulates the target is fed into the reflector from three orthogonal feeds mounted on the inner target axis, at the focal point area of the parabolic reflector. The parabolic reflector, together with the three RF feeds (the Compact Range), effectively produces a far-field image of the target. Both FMT target axis motion and electronic control of the RF beams (deflection) modify the simulated line-of-sight target angles. Multiple targets, glint, multi-path, ECM, and clutter can be introduced electronically. To evaluate dual-mode seekers, the center section of the parabolic reflector is replaced with an IR- transparent, but RF-reflective section. An IR scene projector mounts to the FMT target axes, with its image focused on the intersection of the FMT seeker axes. The system eliminates the need for a large anechoic chamber and 'Target Wall' or target motion system used with conventional HWIL systems. This reduces acquisition and operating costs of the facility.

  17. Influence of Martensite Mechanical Properties on Failure Mode and Ductility of Dual Phase Steels

    SciTech Connect

    Choi, Kyoo Sil; Liu, Wenning N.; Sun, Xin; Khaleel, Mohammad A.

    2009-04-01

    In this paper, the effects of the mechanical properties of the martensite phase on the failure mode and ductility of dual phase (DP) steels are investigated using a micromechanics-based finite element method. Actual microstructures of DP sheet steels obtained from scanning electron microscopy are used as representative volume element (RVE) in two-dimensional plane-stress finite element calculations. Failure is predicted as plastic strain localization in the RVE during deformation. The mechanical properties of the ferrite and martensite phases in a commercial DP 980 steel are obtained based on the in-situ X-ray diffraction measurements of a uniaxial tensile test. Computations are then conducted on the RVE in order to investigate the influence of the martensite mechanical properties and volume fraction on the macroscopic behavior and failure mode of DP steels. The computations show that, as the strength and volume fraction of the martensite phase increase, the ultimate tensile strength (UTS) of DP steels increases but the UTS strain and failure strain decrease. These results agree well with the general experimental observations on DP steels. Additionally, shear dominant failure modes usually develop for DP steels with lower martensite strengths, whereas split failure modes typically develop for DP steels with higher martensite strengths.

  18. Gadolinium photoionization process

    DOEpatents

    Paisner, J.A.; Comaskey, B.J.; Haynam, C.A.; Eggert, J.H.

    1993-04-13

    A method is provided for selective photoionization of the odd-numbered atomic mass gadolinium isotopes 155 and 157. The selective photoionization is accomplished by circular or linear parallel polarized laser beam energy effecting a three-step photoionization pathway.

  19. Gadolinium photoionization process

    DOEpatents

    Paisner, Jeffrey A.; Comaskey, Brian J.; Haynam, Christopher A.; Eggert, Jon H.

    1993-01-01

    A method is provided for selective photoionization of the odd-numbered atomic mass gadolinium isotopes 155 and 157. The selective photoionization is accomplished by circular or linear parallel polarized laser beam energy effecting a three-step photoionization pathway.

  20. Design and multifidelity analysis of dual mode scramjet compression system using coupled NPSS and fluent simulation

    NASA Astrophysics Data System (ADS)

    Vijayakumar, Nandakumar

    Hypersonic airbreathing engines mark a potential future development of the aerospace industry and immense efforts have been taken in gaining knowledge in them for the past decades. The physical phenomenon occurring at the hypersonic flow regime makes the design and performance prediction of a scramjet engine hard. Though cutting-edge simulation tools fight their way toward accurate prediction of the environment, the time consumed by the entire process in designing and analyzing a scramjet engine and its component may be exorbitant. A multi-fidelity approach for designing a scramjet with a cruising Mach number of 6 is detailed in this research where high-order simulations are applied according to the physics involved in the component. Two state-of-the-art simulation tools were used to take the aerodynamic and propulsion disciplines into account for realistic prediction of the individual components as well as the entire scramjet. The specific goal of this research is to create a virtual environment to design and analyze a hypersonic, two-dimensional, planar inlet and isolator to check its operability for a dual-mode scramjet engine. The dual mode scramjet engine starts at a Mach number of 3.5 where it operates as a ramjet and accelerates to Mach 6 to be operated as a scramjet engine. The intercomponent interaction between the compression components with the rest of the engine is studied by varying the fidelity of the numerical simulation according to the complexity of the situation. Efforts have been taken to track the transition Mach number as it switches from ramjet to scramjet. A complete scramjet assembly was built using the Numerical Propulsion Simulation System (NPSS) and the performance of the engine was evaluated for various scenarios. Different numerical techniques were opted for varying the fidelity of the analysis with the highest fidelity consisting of 2D RANS CFD simulation. The interaction between the NPSS elements with the CFD solver is governed by the

  1. Dual mode antibacterial activity of ion substituted calcium phosphate nanocarriers for bone infections.

    PubMed

    Sampath Kumar, T S; Madhumathi, K; Rubaiya, Y; Doble, Mukesh

    2015-01-01

    Nanotechnology has tremendous potential for the management of infectious diseases caused by multi-drug resistant bacteria, through the development of newer antibacterial materials and efficient modes of antibiotic delivery. Calcium phosphate (CaP) bioceramics are commonly used as bone substitutes due to their similarity to bone mineral and are widely researched upon for the treatment of bone infections associated with bone loss. CaPs can be used as local antibiotic delivery agents for bone infections and can be substituted with antibacterial ions in their crystal structure to have a wide spectrum, sustained antibacterial activity even against drug resistant bacteria. In the present work, a dual mode antibiotic delivery system with antibacterial ion substituted calcium deficient hydroxyapatite (CDHA) nanoparticles has been developed. Antibacterial ions such as zinc, silver, and strontium have been incorporated into CDHA at concentrations of 6, 0.25-0.75, and 2.5-7.5 at. %, respectively. The samples were found to be phase pure, acicular nanoparticles of length 40-50 nm and width 5-6 nm approximately. The loading and release profile of doxycycline, a commonly used antibiotic, was studied from the nanocarriers. The drug release was studied for 5 days and the release profile was influenced by the ion concentrations. The release of antibacterial ions was studied over a period of 21 days. The ion substituted CDHA samples were tested for antibacterial efficacy on Staphylococcus aureus and Escherichia coli by MIC/MBC studies and time-kill assay. AgCDHA and ZnCDHA showed high antibacterial activity against both bacteria, while SrCDHA was weakly active against S. aureus. Present study shows that the antibiotic release can provide the initial high antibacterial activity, and the sustained ion release can provide a long-term antibacterial activity. Such dual mode antibiotic and antibacterial ion release offers an efficient and potent way to treat an incumbent drug

  2. Observation of dual-wavelength solitons and bound states in a nanotube/microfiber mode-locking fiber laser

    NASA Astrophysics Data System (ADS)

    Zeng, C.; Cui, Y. D.; Guo, J.

    2015-07-01

    We report on the experimental observation of dual-wavelength soliton and the phase-locked bound state in an all-fiber laser mode-locked by a carbon nanotubes/microfiber saturable absorber. The operation wavelengths are strongly dependent on the intracavity loss. By adjusting an attenuator to increase the intracavity loss, mode-locking wavelength shifts from 1557 to 1531 nm. With the appropriate pump power and intracavity loss, dual-wavelength solitons are achieved simultaneously. In addition, the phase-locked bound-state solitons are also observed at the two wavelengths. The pulse separation and phase difference are related to the first-order Kelly sidebands.

  3. The effect of curing modes on polymerization contraction stress of a dual cured composite.

    PubMed

    Feng, L; Suh, B I

    2006-01-01

    Although a lower curing rate is often cited as the reason why a chemical cured (CC) dental composite produces lower polymerization contraction stress (PCS) than a light cured (LC) composite, the exact mechanism is still unclear. In addition, the comparison is often made by using different brands of composites. The comparison's fairness is questionable because the two composites have different compositions and preparation procedures. The goal of the present work was to determine if the curing mode alone can produce different PCS. We formulated a dual cured composite and prepared it the same way for both CC and LC modes. We measured PCS by a strain gauge method, shrinkage by a video-imagining technique, degree of conversion (DC) by infrared spectroscopy, and flexural modulus by the three-point bending test. The CC specimens showed lower PCS and lower flexural modulus than the LC specimens, although both possessed an identical chemical composition and physical texture before cure. This finding indicates that the curing mode alone can affect PCS. Because the CC and LC specimens produced a similar shrinkage and DC, the lower modulus is considered to be one of the reasons for the lower stress. Using a structural inhomogeneity model, we explained how a resin composite with an identical DC can have different physical properties such as the modulus. PMID:16047326

  4. Chemiresistive and Gravimetric Dual-Mode Gas Sensor toward Target Recognition and Differentiation.

    PubMed

    Chen, Yan; Zhang, Hao; Feng, Zhihong; Zhang, Hongxiang; Zhang, Rui; Yu, Yuanyuan; Tao, Jin; Zhao, Hongyuan; Guo, Wenlan; Pang, Wei; Duan, Xuexin; Liu, Jing; Zhang, Daihua

    2016-08-24

    We demonstrate a dual-mode gas sensor for simultaneous and independent acquisition of electrical and mechanical signals from the same gas adsorption event. The device integrates a graphene field-effect transistor (FET) with a piezoelectric resonator in a seamless manner by leveraging multiple structural and functional synergies. Dual signals resulting from independent physical processes, i.e., mass attachment and charge transfer can reflect intrinsic properties of gas molecules and potentially enable target recognition and quantification at the same time. Fabrication of the device is based on standard Integrated Circuit (IC) foundry processes and fully compatible with system-on-a-chip (SoC) integration to achieve extremely small form factors. In addition, the ability of simultaneous measurements of mass adsorption and charge transfer guides us to a more precise understanding of the interactions between graphene and various gas molecules. Besides its practical functions, the device serves as an effective tool to quantitatively investigate the physical processes and sensing mechanisms for a large library of sensing materials and target analytes. PMID:27455947

  5. A Dual Mode Pulsed Electro-Magnetic Cell Stimulator Produces Acceleration of Myogenic Differentiation

    PubMed Central

    Leon-Salas, Walter D.; Rizk, Hatem; Mo, Chenglin; Weisleder, Noah; Brotto, Leticia; Abreu, Eduardo; Brotto, Marco

    2013-01-01

    This paper presents the design and test of a dual-mode electric and magnetic biological stimulator (EM-Stim). The stimulator generates pulsing electric and magnetic fields at programmable rates and intensities. While electric and magnetic stimulators have been reported before, this is the first device that combines both modalities. The ability of the dual stimulation to target bone and muscle tissue simultaneously has the potential to improve the therapeutic treatment of osteoporosis and sarcopenia. The device is fully programmable, portable and easy to use, and can run from a battery or a power supply. The device can generate magnetic fields of up to 1.6 mT and output voltages of +/−40 V. The EM-Stim accelerated myogenic differentiation of myoblasts into myotubes as evidenced by morphometric, gene expression, and protein content analyses. Currently, there are many patents concerned with the application of single electrical or magnetic stimulation, but none that combine both simultaneously. However, we applied for and obtained a provisional patent for new device to fully explore its therapeutic potential in pre-clinical models. PMID:23445453

  6. The effects of voice and manual control mode on dual task performance

    NASA Technical Reports Server (NTRS)

    Wickens, C. D.; Zenyuh, J.; Culp, V.; Marshak, W.

    1986-01-01

    Two fundamental principles of human performance, compatibility and resource competition, are combined with two structural dichotomies in the human information processing system, manual versus voice output, and left versus right cerebral hemisphere, in order to predict the optimum combination of voice and manual control with either hand, for time-sharing performance of a dicrete and continuous task. Eight right handed male subjected performed a discrete first-order tracking task, time-shared with an auditorily presented Sternberg Memory Search Task. Each task could be controlled by voice, or by the left or right hand, in all possible combinations except for a dual voice mode. When performance was analyzed in terms of a dual-task decrement from single task control conditions, the following variables influenced time-sharing efficiency in diminishing order of magnitude, (1) the modality of control, (discrete manual control of tracking was superior to discrete voice control of tracking and the converse was true with the memory search task), (2) response competition, (performance was degraded when both tasks were responded manually), (3) hemispheric competition, (performance degraded whenever two tasks were controlled by the left hemisphere) (i.e., voice or right handed control). The results confirm the value of predictive models invoice control implementation.

  7. Magnetite loaded Polypeptide-PLGA multifunctional microbubbles for dual-mode US/MR imaging.

    PubMed

    Sun, Ying; Zhu, Yunkai; Huang, Can; Li, Rongxin; Chen, Yaqing; Duan, Yourong

    2016-01-01

    Magnetite loaded Polypeptide-PLGA multifunctional microbubbles (Fe3O4 /Polypeptide-PLGA MMBs) that show superparamagnetic properties were prepared by a modified double emulsion method and employed as imaging agent for dual-mode Ultrasound/Magnetic resonance (US/MR) imaging of prostatic cancer. The successful synthesis of MMBs was determined by Fourier Transform Infrared Spectrometer (FTIR), X-ray diffraction (XRD), Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM), Atomic Absorption Spectroscopy (AAS) and vibrating sample magnetometer (VSM). The as-prepared MMBs had a diameter of 700 nm and were quite safe as confirmed by MTT assays. Prussian Blue Staining showed that targeted Fe3O4 /Polypeptide-PLGA MMBs enhanced the cellular uptake efficiency. In cell attachment study, adherence of MMBs was significantly higher to LNCaP cells compared with negative control PC3 cells. The in vitro results demonstrated that these MMBs could enhance both US and MR imaging of prostatic cancer. PMID:26647349

  8. Dual-Mode HDAC Prodrug for Covalent Modification and Subsequent Inhibitor Release

    PubMed Central

    2016-01-01

    Histone deacetylase inhibitors (HDACi) target abnormal epigenetic states associated with a variety of pathologies, including cancer. Here, the development of a prodrug of the canonical broad-spectrum HDACi suberoylanilide hydroxamic acid (SAHA) is described. Although hydroxamic acids are utilized universally in the development of metalloenzyme inhibitors, they are considered to be poor pharmacophores with reduced activity in vivo. We developed a prodrug of SAHA by appending a promoiety, sensitive to thiols, to the hydroxamic acid warhead (termed SAHA-TAP). After incubation of SAHA-TAP with an HDAC, the thiol of a conserved HDAC cysteine residue becomes covalently tagged with the promoiety, initiating a cascade reaction that leads to the release of SAHA. Mass spectrometry and enzyme kinetics experiments validate that the cysteine residue is covalently appended with the TAP promoiety. SAHA-TAP demonstrates cytotoxicity activity against various cancer cell lines. This strategy represents an original prodrug design with a dual mode of action for HDAC inhibition. PMID:25974739

  9. Dual mode selective chemosensor for copper and fluoride ions: a fluorometric, colorimetric and theoretical investigation.

    PubMed

    Ghosh, Soumen; Ganguly, Aniruddha; Uddin, Md Raihan; Mandal, Sukhendu; Alam, Md Akhtarul; Guchhait, Nikhil

    2016-07-01

    A pyrene containing chemosensor viz. has been designed for the efficient and selective detection of Cu(2+) and F(-) ions in dual sensing mode which do not interfere with each other. The chemosensing behavior of towards Cu(2+) was demonstrated through fluorescence, time resolved fluorescence spectroscopy, and visual fluorescence colour changes, and towards F(-) through naked-eye colour changes, absorption and (1)H NMR titrations. The chemosensor shows excellent selectivity towards Cu(2+) through an excimer switch-off mechanism. Density Functional Theory (DFT) calculations were performed to show the structure and electronic properties of and its copper complex [-Cu(2+)]. The selectivity and sensitivity towards F(-) were explained in terms of H-bonding interactions between and F(-), then deprotonation of . The biological application of has been evaluated in HEK 293 cells and it exhibits good membrane permeability for the detection of Cu(2+). The sensor also shows appreciable sensitivity towards fluoride in toothpaste. PMID:27314977

  10. Experimental Investigation of Reacting Flow Characteristics in a Dual-Mode Scramjet Combustor

    NASA Astrophysics Data System (ADS)

    Shi, Deyong; Song, Wenyan; Ye, Jingfeng; Tao, Bo; Wang, Yanhua

    2016-06-01

    In this work, a hydrogen-fueled dual-mode scramjet combustor was investigated experimentally. Clean and dry air was supplied to the combustor through a Mach 2 nozzle with a total temperature of 800 K and a total pressure of 800 kPa. The high enthalpy air was provided by an electricity resistance heater. Room temperature hydrogen was injected with sonic speed from injector orifices vertically, and downstream the injector a tandem cavity flame holder was mounted. Except wall pressure profiles, velocity and temperature profiles in and at exit of the combustor were also measured using hydroxyl tagging velocimetry (HTV) and tunable diode laser absorption spectroscopy (TDLAS), respectively. Results showed that combustion occurred mainly at the bottom side of the combustor. And there were also an extreme disparity of the velocity and temperature profiles along the Y-direction, i.e. the transverse direction.

  11. A dual-band antenna feed design using a fundamental-mode coupler

    NASA Astrophysics Data System (ADS)

    Carpenter, Earl

    1992-03-01

    By means of a feed system that uses 0-dB directional couplers to inject 11- and 14 GHz fundamental mode signals into a 54-mm diameter circular waveguide, the present dual-feed system allows an earth station antenna to simultaneously operate in the 4/6 GHz and 11/14 GHz Intelsat bands. Since the 4/6 GHz signals can propagate through the Ku-band couplers with only minor perturbations, this approach permits the use of a simple C-band diplexing and polarization network that is low cost and compact, as well as adaptable for various applications. Attention is given to measured performance levels for this system; compatibility with Intelsat is demonstrated.

  12. Dual-mode bioenabled nano-plasmonic sensors for biological and chemical detection

    NASA Astrophysics Data System (ADS)

    Kong, Xianming; Squire, Kenny; Xi, Yuting; LeDuff, Paul; Rorrer, Gregory L.; Wang, Alan X.

    2016-03-01

    Plasmonic biosensors have greatly overcome the limitations of conventional optical sensors in terms of sensitivity, tunability, photo-stability, and in vivo applicability. In this paper, we present plasmonic biosensors using bioenabled nanomaterials diatom biosilica, with active surface functionalities as affordable and eco-friendly integration platforms of Ag nanoparticles for label-free detection of biomolecules. Dual-mode plasmon sensing mechanisms, including surface-enhanced Raman scattering (SERS) and refractive-index (RI) sensing will be simultaneously implemented on the plasmonic-biosilica nanostructures to obtain quantitative biosensing with structural resolution of the biomolecules. We have achieved ultra-sensitive detection of Rhodamine 6G (R6G) at concentrations as low as 10-10 M. Furthermore, this substrate was used to detect TNT, illustrating the potential application as viable substrates for monitoring pollutant and toxics in environment.

  13. Monitoring and guidance of HIFU beams with dual-mode ultrasound arrays.

    PubMed

    Ballard, John R; Casper, Andrew J; Ebbini, Emad S

    2009-01-01

    We present experimental results illustrating the unique advantages of dual-mode array (DMUA) systems in monitoring and guidance of high intensity focused ultrasound (HIFU) lesion formation. DMUAs offer a unique paradigm in image-guided surgery; one in which images obtained using the same therapeutic transducer provide feedback for: 1) refocusing the array in the presence of strongly scattering objects, e.g. the ribs, 2) temperature change at the intended location of the HIFU focus, and 3) changes in the echogenicity of the tissue in response to therapeutic HIFU. These forms of feedback have been demonstrated in vitro in preparation for the design and implementation of a real-time system for imaging and therapy with DMUAs. The results clearly demonstrate that DMUA image feedback is spatially accurate and provide sufficient spatial and contrast resolution for identification of high contrast objects like the ribs and significant blood vessels in the path of the HIFU beam. PMID:19964926

  14. Aggregation-based fuzzy dual-mode control for nonlinear systems with mixed constraints

    NASA Astrophysics Data System (ADS)

    Wen, Jiwei; Liu, Fei

    2012-05-01

    A new receding horizon dual-mode control method is proposed for a class of discrete-time nonlinear systems represented by Takagi-Sugeno (T-S) fuzzy models subject to mixed constraints including hard input constraint and soft state constraint. On the one hand, our receding horizon scheme is based upon an online optimisation that utilises optimised sequence plus local linear feedback. On the other hand, due to the consideration of computation burden, an amplitude decaying aggregation strategy is introduced to reduce the number of optimisation variables. The proposed controller is obtained using semi-definite programming, which can be easily solved by means of linear matrix inequalities. A numerical example is given to verify the feasibility and efficiency of the proposed method.

  15. Carrier recovery methods for a dual-mode modem: A design approach

    NASA Technical Reports Server (NTRS)

    Richards, C. W.; Wilson, S. G.

    1984-01-01

    A dual mode model with selectable QPSK or 16-QASK modulation schemes is discussed. The theoretical reasoning as well as the practical trade-offs made during the development of a modem are presented, with attention given to the carrier recovery method used for coherent demodulation. Particular attention is given to carrier recovery methods that can provide little degradation due to phase error for both QPSK and 16-QASK, while being insensitive to the amplitude characteristic of a 16-QASK modulation scheme. A computer analysis of the degradation is symbol error rate (SER) for QPSK and 16-QASK due to phase error is prresented. Results find that an energy increase of roughly 4 dB is needed to maintain a SER of 1X10(-5) for QPSK with 20 deg of phase error and 16-QASK with 7 deg phase error.

  16. Comments on dual-mode nuclear space power and propulsion system concepts

    NASA Technical Reports Server (NTRS)

    Layton, J. Preston; Grey, Jerry

    1991-01-01

    Some form of Dual-Mode Nuclear Space Power & Propulsion System (D-MNSP&PS) will be essential to spacefaring throughout teh solar system and that such systems must evolve as mankind moves into outer space. The initial D-MNPSP&PS Reference System should be based on (1) present (1990), and (2) advanced (1995) technology for use on comparable mission in the 2000 and 2005 time period respectively. D-MNSP&PS can be broken down into a number of subsystems: Nuclear subsystems including the energy source and controls for the release of thermal power at elevated temperatures; power conversion subsystems; waste heat rejection subsystems; and control and safety subsystems. These systems are briefly detailed.

  17. Combustion stabilization, structure, and spreading in a laboratory dual-mode scramjet combustor

    NASA Astrophysics Data System (ADS)

    Micka, Daniel James

    Dual-mode scramjets have the potential to provide efficient, air-breathing propulsion at high flight Mach numbers. Flame stabilization and spreading are a challenge in such engines due to the very high flow velocities. Combustion occurs in a complex regime where both flame properties and auto-ignition reactions are expected to be important. The focus of the current study is to improve the physical understanding of the combustion mechanism and its practical implication in such combustors. Topics of interest are the combustion stabilization locations, the detailed structure of the reaction zone, and the physical mechanisms controlling the heat release distribution. A facility was developed for the experimental investigation of a laboratory dual-mode scramjet combustor at conditions equivalent to flight Mach numbers of 4.3 to 5.5. The combustor contained flush wall fuel injection and a cavity flameholder, which are the basic flow elements in many proposed practical designs. The diagnostics used include high speed movies of the chemiluminescence, wall pressure measurements, and planar laser induced fluorescence of CH, and simultaneous OH/formaldehyde. The study revealed two distinct reaction zone structures that are caused by two flame anchoring locations. Cavity stabilized combustion occurs at low stagnation temperatures. For these conditions the reaction zone is anchored at the cavity leading edge and the flame spreading is controlled by premixed flame propagation. Jet-wake stabilized combustion occurs at high stagnation temperatures. The reaction zone is a lifted jet flame, which has a premixed base and a downstream diffusion flame. In all cases, initial auto-ignition reactions occur well upstream of the primary reaction zone, resulting in an auto-ignition assisted flame base. The results are useful for developing physics based models of the combustion.

  18. Experimental study on combustion modes and thrust performance of a staged-combustor of the scramjet with dual-strut

    NASA Astrophysics Data System (ADS)

    Yang, Qingchun; Chetehouna, Khaled; Gascoin, Nicolas; Bao, Wen

    2016-05-01

    To enable the scramjet operate in a wider flight Mach number, a staged-combustor with dual-strut is introduced to hold more heat release at low flight Mach conditions. The behavior of mode transition was examined using a direct-connect model scramjet experiment along with pressure measurements. The typical operating modes of the staged-combustor are analyzed. Fuel injection scheme has a significant effect on the combustor operating modes, particularly for the supersonic combustion mode. Thrust performances of the combustor with different combustion modes and fuel distributions are reported in this paper. The first-staged strut injection has a better engine performance in the operation of subsonic combustion mode. On the contrast, the second-staged strut injection has a better engine performance in the operation of supersonic combustion mode.

  19. Real-time dual-comb spectroscopy with a free-running bidirectionally mode-locked fiber laser

    NASA Astrophysics Data System (ADS)

    Mehravar, S.; Norwood, R. A.; Peyghambarian, N.; Kieu, K.

    2016-06-01

    Dual-comb technique has enabled exciting applications in high resolution spectroscopy, precision distance measurements, and 3D imaging. Major advantages over traditional methods can be achieved with dual-comb technique. For example, dual-comb spectroscopy provides orders of magnitude improvement in acquisition speed over standard Fourier-transform spectroscopy while still preserving the high resolution capability. Wider adoption of the technique has, however, been hindered by the need for complex and expensive ultrafast laser systems. Here, we present a simple and robust dual-comb system that employs a free-running bidirectionally mode-locked fiber laser operating at telecommunication wavelength. Two femtosecond frequency combs (with a small difference in repetition rates) are generated from a single laser cavity to ensure mutual coherent properties and common noise cancellation. As the result, we have achieved real-time absorption spectroscopy measurements without the need for complex servo locking with accurate frequency referencing, and relatively high signal-to-noise ratio.

  20. A tunable and switchable single-longitudinal-mode dual-wavelength fiber laser with a simple linear cavity.

    PubMed

    He, Xiaoying; Fang, Xia; Liao, Changrui; Wang, D N; Sun, Junqiang

    2009-11-23

    A simple linear cavity erbium-doped fiber laser based on a Fabry-Perot filter which consists of a pair of fiber Bragg gratings is proposed for tunable and switchable single-longitudinal-mode dual-wavelength operation. The single-longitudinal-mode is obtained by the saturable absorption of an unpumed erbium-doped fiber together with a narrow-band fiber Bragg grating. Under the high pump power (>166 mW) condition, the stable dual-wavelength oscillation with uniform amplitude can be realized by carefully adjusting the polarization controller in the cavity. Wavelength selection and switching are achieved by tuning the narrow-band fiber Bragg grating in the system. The spacing of the dual-wavelength can be selected at 0.20 nm (approximately 25.62 GHz), 0.22 nm (approximately 28.19 GHz) and 0.54 nm (approximately 69.19 GHz). PMID:19997420

  1. Erbium-doped fiber triple-ring laser configuration with single-longitudinal-mode dual-wavelength output

    NASA Astrophysics Data System (ADS)

    Yeh, Chien-Hung; Chen, Hone-Zhang; Chen, Jhih-Yu; Tsai, Ning; Zhuang, Yuan-Hong; Chen, Jing-Heng; Lin, Fey

    2016-02-01

    In this investigation, we propose and demonstrate a stabilized single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber (EDF) laser triple-ring cavity. Here, two fiber Bragg gratings (FBGs) are used inside the fiber cavity to generate dual-wavelength output. In order to complete the SLM output, the triple-ring configuration is utilized for suppressing the densely multi-longitudinal mode (MLM). The output powers and wavelengths of  -8.4 and  -8.5 dBm and 1535.76 and 1543.28 nm are obtained in the proposed dual-wavelength EDF laser, respectively. Moreover, the stability performances of output power and wavelength in the proposed EDF laser are also discussed.

  2. Solvent-dependent dual-mode photochromism between T- and P-types in a dipyrrinone derivative.

    PubMed

    Sakata, Yoko; Fukushima, Satomi; Akine, Shigehisa; Setsune, Jun-ichiro

    2016-01-21

    A newly synthesized dipyrrinone derivative bearing an ethoxycarbonyl group at the pyrrolic-α position exhibited solvent-dependent dual-mode photochromism between T- and P-types. While this molecule underwent thermally reversible (T-type) photoresponsive reaction in chloroform, it became a thermally irreversible (P-type) system in methanol. PMID:26615770

  3. Fatigue Failure Modes of the Grain Size Transition Zone in a Dual Microstructure Disk

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Kantzos, Pete T.; Palsa, Bonnie; Telesman, Jack; Gayda, John; Sudbrack, Chantal K.

    2012-01-01

    Mechanical property requirements vary with location in nickel-based superalloy disks. In order to maximize the associated mechanical properties, heat treatment methods have been developed for producing tailored grain microstructures. In this study, fatigue failure modes of a grain size transition zone in a dual microstructure disk were evaluated. A specialized heat treatment method was applied to produce varying grain microstructure in the bore to rim portions of a powder metallurgy processed nickel-based superalloy disk. The transition in grain size was concentrated in a zone of the disk web, between the bore and rim. Specimens were extracted parallel and transversely across this transition zone, and multiple fatigue tests were performed at 427 C and 704 C. Grain size distributions were characterized in the specimens, and related to operative failure initiation modes. Mean fatigue life decreased with increasing maximum grain size, going out through the transition zone. The scatter in limited tests of replicates was comparable for failures of uniform gage specimens in all transition zone locations examined.

  4. Dual pumping of magnetostatic and spin-wave modes in yttrium-iron-garnet spheres

    NASA Astrophysics Data System (ADS)

    Araújo, W.; de Aguiar, F. M.; Azevedo, A.; Rezende, S. M.

    2003-05-01

    In ferrimagnetic materials subjected to a static magnetic field H, a parallel rf magnetic field h gives rise to nonlinear absorption due to the unstable growth of certain spin waves when exceeding a parametric instability threshold (PIT), h=hc. The excited spin waves have half the pumping frequency and a wave number k that depends on H, such that the curve hc vs H resembles the Greek symbol ν and is thus called a "butterfly curve." Recent experiments in a yttrium-iron-garnet sphere have shown that the PIT is resonantly reduced in the presence of a simultaneous perpendicular rf field at half the parallel-pumping frequency only on the right wing of the butterfly curve, where "volume" magnetostatic modes (k˜0) are primarily excited. Here, dual pumping experiments are reported at lower frequencies (8.882 and 4.441 GHz), allowing the presence of "surface" magnetostatic modes on the left wing and corresponding resonant PIT reduction in that region, where spin waves with k˜105 cm-1 are primarily excited by the parallel-pumping field. The results qualitatively agree with a model that put no restriction on the pumping frequency, thus extending earlier calculations by White and Schlömann [R. M. White and Schlömann, J. Appl. Phys. 33, 2437 (1962)].

  5. A dual-mode disturbance-accommodating controller for the Hubble Space Telescope

    NASA Astrophysics Data System (ADS)

    Addington, Stewart; Johnson, C. D.

    Cyclic thermal expansions and mechanical stiction effects in the Solar Arrays on the Hubble Space Telescope (HST) are triggering repeated occurrences of damped, relaxation-type flex-body vibrations of the solar arrays. Those solar array vibrations are, in turn, causing unwanted, oscillating disturbance torques on the HST main body, which cause unwanted deviations of the telescope from its specified pointing direction. In this paper we propose two strategies one can adopt in designing a telescope-pointing controller to cope with the aforementioned disturbances: (1) a `total isolation' (TI) control strategy whereby the HST controller torques are designed to adaptively counteract and cancel-out the persistent disturbing torques that are causing the unwanted telescope motions, and (2) an `array damping' (AD) control strategy whereby the HST controller torques are used to actively augment the natural dampening of the solar array vibrations and the attendant telescope motions, between triggerings of the stiction-related flex-body relaxation oscillations. Using the principles of Disturbance-Accommodating Control (DAC) Theory a dual-mode controller for a generic, planar-motion (single-axis) model of the HST is proposed. This controller incorporates both the TI and AD modes of disturbance-accommodation. Simulation studies of the closed-loop system using generic parameter values clearly indicate, qualitatively, the enhanced pointing-performance such a controller can achieve.

  6. Dual-mode disturbance-accommodating pointing controller for Hubble Space Telescope

    NASA Astrophysics Data System (ADS)

    Addington, Stewart I.; Johnson, C. D.

    1995-03-01

    Cyclic thermal expansions and mechanical stiction effects in the solar arrays on the Hubble Space Telescope (HST) are triggering repeated occurrences of damped, relaxation-type flex-body vibrations of the solar arrays. Those solar array vibrations are, in turn, causing unwanted deviations of the telescope from its specified pointing direction. In this paper we propose two strategies one can adopt in designing a telescope-pointing controller to cope with the aforementioned disturbances: 1) a total isolation (TI) control strategy whereby the HST controller torques are designed to adaptively counteract and cancel out the persistent disturbing torques that are causing the unwanted telescope motions and 2) an array damping (AD) control strategy whereby the HST controller torques are used to actively augment the natural dampening of the solar array vibrations and the attendant telescope motions, between triggerings of the stiction-related flex-body relaxation oscillations. Using the principles of disturbance accommodation control theory, a dual-mode controller for a generic, planar-motion (single-axis) model of the HST is proposed. This controller incorporates both the TI and AD modes of disturbance accommodation. Simulation studies of the closed-loop system using generic parameter values clearly indicate, qualitatively, the enhanced pointing performance such a controller can achieve.

  7. Dual Mode Antibacterial Activity of Ion Substituted Calcium Phosphate Nanocarriers for Bone Infections

    PubMed Central

    Sampath Kumar, T. S.; Madhumathi, K.; Rubaiya, Y.; Doble, Mukesh

    2015-01-01

    Nanotechnology has tremendous potential for the management of infectious diseases caused by multi-drug resistant bacteria, through the development of newer antibacterial materials and efficient modes of antibiotic delivery. Calcium phosphate (CaP) bioceramics are commonly used as bone substitutes due to their similarity to bone mineral and are widely researched upon for the treatment of bone infections associated with bone loss. CaPs can be used as local antibiotic delivery agents for bone infections and can be substituted with antibacterial ions in their crystal structure to have a wide spectrum, sustained antibacterial activity even against drug resistant bacteria. In the present work, a dual mode antibiotic delivery system with antibacterial ion substituted calcium deficient hydroxyapatite (CDHA) nanoparticles has been developed. Antibacterial ions such as zinc, silver, and strontium have been incorporated into CDHA at concentrations of 6, 0.25–0.75, and 2.5–7.5 at. %, respectively. The samples were found to be phase pure, acicular nanoparticles of length 40–50 nm and width 5–6 nm approximately. The loading and release profile of doxycycline, a commonly used antibiotic, was studied from the nanocarriers. The drug release was studied for 5 days and the release profile was influenced by the ion concentrations. The release of antibacterial ions was studied over a period of 21 days. The ion substituted CDHA samples were tested for antibacterial efficacy on Staphylococcus aureus and Escherichia coli by MIC/MBC studies and time-kill assay. AgCDHA and ZnCDHA showed high antibacterial activity against both bacteria, while SrCDHA was weakly active against S. aureus. Present study shows that the antibiotic release can provide the initial high antibacterial activity, and the sustained ion release can provide a long-term antibacterial activity. Such dual mode antibiotic and antibacterial ion release offers an efficient and potent way to treat an incumbent

  8. Architecture of GnRH-Gonadotrope-Vasculature Reveals a Dual Mode of Gonadotropin Regulation in Fish.

    PubMed

    Golan, Matan; Zelinger, Einat; Zohar, Yonathan; Levavi-Sivan, Berta

    2015-11-01

    The function and components of the hypothalamic-pituitary axis are conserved among vertebrates; however, in fish, a neuroglandular mode of delivery (direct contact between axons and endocrine cells) was considered dominant, whereas in tetrapods hypothalamic signals are relayed to their targets via the hypophysial portal blood system (neurovascular delivery mode). By using a transgenic zebrafish model we studied the functional and anatomical aspects of gonadotrope regulation thus revisiting the existing model. FSH cells were found to be situated close to the vasculature whereas the compact organization of LH cells prevented direct contact of all cells with the circulation. GnRH3 fibers formed multiple boutons upon reaching the pituitary, but most of these structures were located in the neurohypophysis rather than adjacent to gonadotropes. A close association was observed between FSH cells and GnRH3 boutons, but only a fifth of the LH cells were in direct contact with GnRH3 axons, suggesting that FSH cells are more directly regulated than LH cells. GnRH3 fibers closely followed the vasculature in the neurohypophysis and formed numerous boutons along these tracts. These vessels were found to be permeable to relatively large molecules, suggesting the uptake of GnRH3 peptides. Our findings have important implications regarding the differential regulation of LH and FSH and contradict the accepted notion that fish pituitary cells are mostly regulated directly by hypothalamic fibers. Instead, we provide evidence that zebrafish apply a dual mode of gonadotrope regulation by GnRH3 that combines both neuroglandular and neurovascular components. PMID:26261873

  9. Mechanically tunable organic vertical-cavity surface emitting lasers (VCSELs) for highly sensitive stress probing in dual-modes.

    PubMed

    Yang, Yu; Zhou, Yuan; Liao, Zhifu; Yu, Jiancan; Cui, Yuanjing; Garcia-Moreno, Inmaculada; Wang, Zhiyu; Costela, Angel; Qian, Guodong

    2015-02-23

    Herein, we report a straight forward stress probing method based on mechanically tunable organic VCSELs via dual detecting-modes. By designing the active layer thickness, uploaded stress was measured simultaneously by the laser wavelength and mode separations, facilitating highly sensitive stress detection in broad ranges. Single-mode laser emission with low threshold and narrow line-width was characterized, which could be tuned continuously within 8 nm. The probing sensitivity and resolution were estimated to be 60 Pa and 5.6 nm/KPa respectively, which were ~160-folds higher than previous results. PMID:25836475

  10. Probing the fundamental limit of niobium in high radiofrequency fields by dual mode excitation in superconducting radiofrequency cavities

    SciTech Connect

    Eremeev, Grigory; Geng, Rongli; Palczewski, Ari

    2011-07-01

    We have studied thermal breakdown in several multicell superconducting radiofrequency cavity by simultaneous excitation of two TM{sub 010} passband modes. Unlike measurements done in the past, which indicated a clear thermal nature of the breakdown, our measurements present a more complex picture with interplay of both thermal and magnetic effects. JLab LG-1 that we studied was limited at 40.5 MV/m, corresponding to B{sub peak} = 173 mT, in 8{pi}/9 mode. Dual mode measurements on this quench indicate that this quench is not purely magnetic, and so we conclude that this field is not the fundamental limit in SRF cavities.

  11. Dual-head lithotripsy in synchronous mode: Acute effect on renal function and morphology in the pig

    PubMed Central

    Handa, Rajash K.; McAteer, James A.; Willis, Lynn R.; Pishchalnikov, Yuri A.; Connors, Bret A.; Ying, Jun; Lingeman, James E.; Evan, Andrew P.

    2008-01-01

    Objective Lithotripters with two shock heads are now available for use in treating patients. However, little information is available by which to judge the safety of treatment with dual pulses. A study was conducted to assess the effect of dual-head lithotripsy on renal function and morphology in a pig model of shock wave (SW) injury. Methods A dual-head electrohydraulic lithotripter (Direx Duet) was used to treat the lower renal pole of anesthetized pigs with a clinical dose of SWs (2400 dual SWs; n=10) delivered in synchronous mode (i.e. both heads fired simultaneously). For comparison, pigs were treated with either 2400 SWs (n=12) or 4800 SWs (n=8) with a conventional electrohydraulic lithotripter (Dornier HM3). Results Dual SW treatment with the Duet lithotripter caused a decline in glomerular filtration rate (GFR, 4.1 ± 1.9 ml/min) with a trend for effective renal plasma flow (RPF, 31 ± 19 ml/min) to also fall. These changes in renal hemodynamics were comparable to decreases in GFR and RPF in response to treatment with 2400 SWs (4.8 ± 0.8 ml/min and 32 ± 10 ml/min, respectively) or 4800 SWs (5.4 ± 1.0 ml/min and 68 ± 14 ml/min, respectively) with the HM3 lithotripter. Linear association analysis showed that the functional response to dual-pulse SWs was less predictable than with conventional SWs. Morphological quantitation of kidney damage expressed as percentage of functional renal volume (FRV), showed that tissue injury with 2400 paired SWs with the Duet (0.96± 0.39% FRV, n=8) was comparable to injury produced by either 2400 single SWs (1.08±0.38% FRV, n=6), or 4800 single SWs (2.71±1.02% FRV, n=6) with the HM3. However, morphological damage appeared less consistent with the Duet (measurable in only 5 of 8 kidneys) than that observed with the HM3 (measurable in all 12 kidneys). Acoustic output and the timing of dual SWs in synchronous mode increased in variability as the electrodes aged, affecting the amplitude and targeting of focal pressures

  12. Dual mode diffusion of NaCl in Japanese radish under cooking conditions.

    PubMed

    Hashiba, H; Komiyama, J; Nakanishi, T; Gocho, H

    2007-04-01

    Sorption and diffusion of NaCl in Japanese radish have been studied. The sorption isotherm was obtained at 98 degrees C by the conventional method. The concentration profile by the 1-dimensional diffusion of NaCl in Japanese radish from the 3.0% solution was measured at 98 degrees C with the FRITRUC method involving a foodstuff rod in a thin rubber casing. Fick's diffusion coefficient, D, calculated therefrom showed a threefold variation with a maximum. This variation was quantitatively interpreted by applying a dual-mode sorption and diffusion theory under an assumption that the rate determining step of the diffusion is that in the cell wall. Two thermodynamic diffusion coefficients, D(T)(p) and D(T)(L), where p and L are the species of NaCl sorbed by partition and Langmuir modes, respectively, a parameter, alpha, derived from the local equilibrium relations between the p and L species, and S, the concentration of the Langmuir adsorption site in the cell wall of the radish, were estimated. D(T)(p) was found to be smaller than D(T)(L). As an explanation of the larger D(T)(L), we invoked the higher hydration state of the adsorption site of the L species, being ascribed to residual anionic pectin in the radish than the local environment of the p species. The sorption isotherm showed a convex upward deviation from the linear relation. By using the parameters for the local equilibrium and some assumed parameters, the isotherm was found to be explainable. We suggest possible applications of the present method and interpretation to the diffusion study on the cooking systems comprising varieties of seasoning components and foodstuffs. PMID:17995794

  13. Dual-mode wavefront detection sensor based on liquid crystal microlens array

    NASA Astrophysics Data System (ADS)

    Li, Hui; Pan, Fan; Liu, Kan; Wu, Yuntao; Zhang, Yanduo; Xie, Xiaolin

    2014-10-01

    Based on a proposed electrically tunable liquid crystal (LC) micro-lens array (MLA) instead of a commonly used microlens array with fixed focal length in a conventional type, a new prototyped Shack-Hartmann sensor is reported. The LCMLA with 128 × 128 elements is fabricated by the methods of photolithography and hydrochloric acid etching. Composed of the proposed LC-MLA and a CCD, a new type Shack-Hartmann wavefront sensor is got. This kind sensor can solve problems of the tradition wavefront sensor that the larger measurement range and high measurement accurate can't be realized by the same device. Except for adaptive switching the two working modes, this wavefront sensor also has a dual-mode imaging feature with obtaining wavefront information of the target and it's two-dimensional optical intensity image at the same time. In order to verify it's characteristics, an extreme experiment is designed, which introduces a distortion wavefront. At this circumstanc, the traditional wavefront sensor can't get anything. However, with proposed wavefront sensor, this situation can be solved by adjusting the applied voltage of LC-MLA to change it's focal length. With a reconstruction method, the three-dimensional information of the wavefront can be got. At the same time, the two-dimensional optical intensity image is also got. From the experiments, we can prove that it can effectively improve detection sensitivity and dynamic measurement range of wavefront. Results of the prototype demonstrated qualitatively verify this feasibility. This kind new type wavefront sensor will have a wide variety of applications in adaptive optics.

  14. A dual-mode operation overmoded coaxial millimeter-wave generator with high power capacity and pure transverse electric and magnetic mode output

    NASA Astrophysics Data System (ADS)

    Bai, Zhen; Zhang, Jun; Zhong, Huihuang

    2016-04-01

    An overmoded coaxial millimeter-wave generator with high power capacity and pure transverse electric and magnetic (TEM) mode output is designed and presented, by using a kind of coaxial slow wave structure (SWS) with large transversal dimension and small distance between inner and outer conductors. The generator works in dual-mode operation mechanism. The electron beam synchronously interacts with 7π/8 mode of quasi-TEM, at the meanwhile exchanges energy with 3π/8 mode of TM01. The existence of TM01 mode, which is traveling wave, not only increases the beam-wave interaction efficiency but also improves the extraction efficiency. The large transversal dimension of coaxial SWS makes its power capacity higher than that of other reported millimeter-wave devices and the small distance between inner and outer conductors allows only two azimuthally symmetric modes to coexist. The converter after the SWS guarantees the mode purity of output power. Particle-in-cell simulation shows that when the diode voltage is 400 kV and beam current is 3.8 kA, the generation of microwave at 32.26 GHz with an output power of 611 MW and a conversion efficiency of 40% is obtained. The power percentage carried by TEM mode reaches 99.7% in the output power.

  15. New Class of HIV-1 Integrase (IN) Inhibitors with a Dual Mode of Action

    PubMed Central

    Tsiang, Manuel; Jones, Gregg S.; Niedziela-Majka, Anita; Kan, Elaine; Lansdon, Eric B.; Huang, Wayne; Hung, Magdeleine; Samuel, Dharmaraj; Novikov, Nikolai; Xu, Yili; Mitchell, Michael; Guo, Hongyan; Babaoglu, Kerim; Liu, Xiaohong; Geleziunas, Romas; Sakowicz, Roman

    2012-01-01

    tert-Butoxy-(4-phenyl-quinolin-3-yl)-acetic acids (tBPQA) are a new class of HIV-1 integrase (IN) inhibitors that are structurally distinct from IN strand transfer inhibitors but analogous to LEDGINs. LEDGINs are a class of potent antiviral compounds that interacts with the lens epithelium-derived growth factor (LEDGF) binding pocket on IN and were identified through competition binding against LEDGF. LEDGF tethers IN to the host chromatin and enables targeted integration of viral DNA. The prevailing understanding of the antiviral mechanism of LEDGINs is that they inhibit LEDGF binding to IN, which prevents targeted integration of HIV-1. We showed that in addition to the properties already known for LEDGINs, the binding of tBPQAs to the IN dimer interface inhibits IN enzymatic activity in a LEDGF-independent manner. Using the analysis of two long terminal repeat junctions in HIV-infected cells, we showed that the inhibition by tBPQAs occurs at or prior to the viral DNA 3′-processing step. Biochemical studies revealed that this inhibition operates by compound-induced conformational changes in the IN dimer that prevent proper assembly of IN onto viral DNA. For the first time, tBPQAs were demonstrated to be allosteric inhibitors of HIV-1 IN displaying a dual mode of action: inhibition of IN-viral DNA assembly and inhibition of IN-LEDGF interaction. PMID:22535962

  16. New class of HIV-1 integrase (IN) inhibitors with a dual mode of action.

    PubMed

    Tsiang, Manuel; Jones, Gregg S; Niedziela-Majka, Anita; Kan, Elaine; Lansdon, Eric B; Huang, Wayne; Hung, Magdeleine; Samuel, Dharmaraj; Novikov, Nikolai; Xu, Yili; Mitchell, Michael; Guo, Hongyan; Babaoglu, Kerim; Liu, Xiaohong; Geleziunas, Romas; Sakowicz, Roman

    2012-06-15

    tert-Butoxy-(4-phenyl-quinolin-3-yl)-acetic acids (tBPQA) are a new class of HIV-1 integrase (IN) inhibitors that are structurally distinct from IN strand transfer inhibitors but analogous to LEDGINs. LEDGINs are a class of potent antiviral compounds that interacts with the lens epithelium-derived growth factor (LEDGF) binding pocket on IN and were identified through competition binding against LEDGF. LEDGF tethers IN to the host chromatin and enables targeted integration of viral DNA. The prevailing understanding of the antiviral mechanism of LEDGINs is that they inhibit LEDGF binding to IN, which prevents targeted integration of HIV-1. We showed that in addition to the properties already known for LEDGINs, the binding of tBPQAs to the IN dimer interface inhibits IN enzymatic activity in a LEDGF-independent manner. Using the analysis of two long terminal repeat junctions in HIV-infected cells, we showed that the inhibition by tBPQAs occurs at or prior to the viral DNA 3'-processing step. Biochemical studies revealed that this inhibition operates by compound-induced conformational changes in the IN dimer that prevent proper assembly of IN onto viral DNA. For the first time, tBPQAs were demonstrated to be allosteric inhibitors of HIV-1 IN displaying a dual mode of action: inhibition of IN-viral DNA assembly and inhibition of IN-LEDGF interaction. PMID:22535962

  17. Dual-mode optical microscope based on single-pixel imaging

    NASA Astrophysics Data System (ADS)

    Rodríguez, A. D.; Clemente, P.; Tajahuerce, E.; Lancis, J.

    2016-07-01

    We demonstrate an inverted microscope that can image specimens in both reflection and transmission modes simultaneously with a single light source. The microscope utilizes a digital micromirror device (DMD) for patterned illumination altogether with two single-pixel photosensors for efficient light detection. The system, a scan-less device with no moving parts, works by sequential projection of a set of binary intensity patterns onto the sample that are codified onto a modified commercial DMD. Data to be displayed are geometrically transformed before written into a memory cell to cancel optical artifacts coming from the diamond-like shaped structure of the micromirror array. The 24-bit color depth of the display is fully exploited to increase the frame rate by a factor of 24, which makes the technique practicable for real samples. Our commercial DMD-based LED-illumination is cost effective and can be easily coupled as an add-on module for already existing inverted microscopes. The reflection and transmission information provided by our dual microscope complement each other and can be useful for imaging non-uniform samples and to prevent self-shadowing effects.

  18. Microscale characterization of the viscoelastic properties of hydrogel biomaterials using dual-mode ultrasound elastography.

    PubMed

    Hong, Xiaowei; Stegemann, Jan P; Deng, Cheri X

    2016-05-01

    Characterization of the microscale mechanical properties of biomaterials is a key challenge in the field of mechanobiology. Dual-mode ultrasound elastography (DUE) uses high frequency focused ultrasound to induce compression in a sample, combined with interleaved ultrasound imaging to measure the resulting deformation. This technique can be used to non-invasively perform creep testing on hydrogel biomaterials to characterize their viscoelastic properties. DUE was applied to a range of hydrogel constructs consisting of either hydroxyapatite (HA)-doped agarose, HA-collagen, HA-fibrin, or preosteoblast-seeded collagen constructs. DUE provided spatial and temporal mapping of local and bulk displacements and strains at high resolution. Hydrogel materials exhibited characteristic creep behavior, and the maximum strain and residual strain were both material- and concentration-dependent. Burger's viscoelastic model was used to extract characteristic parameters describing material behavior. Increased protein concentration resulted in greater stiffness and viscosity, but did not affect the viscoelastic time constant of acellular constructs. Collagen constructs exhibited significantly higher modulus and viscosity than fibrin constructs. Cell-seeded collagen constructs became stiffer with altered mechanical behavior as they developed over time. Importantly, DUE also provides insight into the spatial variation of viscoelastic properties at sub-millimeter resolution, allowing interrogation of the interior of constructs. DUE presents a novel technique for non-invasively characterizing hydrogel materials at the microscale, and therefore may have unique utility in the study of mechanobiology and the characterization of hydrogel biomaterials. PMID:26928595

  19. Velocity Measurement in a Dual-Mode Supersonic Combustor using Particle Image Velocimetry

    NASA Technical Reports Server (NTRS)

    Goyne, C. P.; McDaniel, J. C.; Krauss, R. H.; Day, S. W.; Reubush, D. E. (Technical Monitor); McClinton, C. R. (Technical Monitor); Reubush, D. E.

    2001-01-01

    Temporally and spatially-resolved, two-component measurements of velocity in a supersonic hydrogen-air combustor are reported. The combustor had a single unswept ramp fuel injector and operated with an inlet Mach number of 2 and a flow total temperature approaching 1200 K. The experiment simulated the mixing and combustion processes of a dual-mode scramjet operating at a flight Mach number near 5. The velocity measurements were obtained by seeding the fuel with alumina particles and performing Particle Image Velocimetry on the mixing and combustion wake of the ramp injector. To assess the effects of combustion on the fuel air-mixing process, the distribution of time-averaged velocity and relative turbulence intensity was determined for the cases of fuel-air mixing and fuel-air reacting. Relative to the mixing case, the near field core velocity of the reacting fuel jet had a slower streamwise decay. In the far field, downstream of 4 to 6 ramp heights from the ramp base, the heat release of combustion resulted in decreased flow velocity and increased turbulence levels. The reacting measurements were also compared with a computational fluid dynamics solution of the flow field. Numerically predicted velocity magnitudes were higher than that measured and the jet penetration was lower.

  20. Preparation and evaluation of dual-mode floating gastroretentive tablets containing itraconazole.

    PubMed

    Kim, Ju-Young; Rhee, Yun-Seok; Park, Chun-Woong; Ha, Jung-Myung; Park, Eun-Seok

    2014-11-01

    The aims of the present study were to prepare new dual-mode floating gastroretentive tablets (DF-GRT) containing itraconazole (ITR) and to evaluate influence of the dosage forms on pharmacokinetic parameters of ITR. The solubility of ITR was enhanced around 200 times (from 1.54 to 248.38 µg/mL) by preparing solid dispersion (SD) with hydroxypropylmethyl cellulose. Buoyancy of DF-GRT containing ITR-SD was established by both camphor sublimation and gas generation. Camphor sublimation decreased density of DF-GRT by making pores in tablet matrix, which led to elimination of lag time for floating. Carbon dioxide generated by sodium bicarbonate and citric acid helped to maintain buoyancy of DF-GRT. Therefore DF-GRT floated on the medium without lag time until disintegrated entirely during in vitro release study. They released 89.11% of the drug at 2 h. Residual camphor was <0.5 wt% after sublimation. The pharmacokinetics of DF-GRT was evaluated in six miniature pigs and compared to immediate release tablets (IRT). Mean AUC ratio of GRT/IRT was 1.36 but there was no statistical difference between AUC values. However delayed tmax, increased MRT and equivalent Cmax of DF-GRT supposed it could be a promising tool for gastroretentive drug delivery system containing ITR. PMID:24245857

  1. Dual-mode ion switching conducting polymer films as high energy supercapacitor materials

    SciTech Connect

    Naoi, Katsuhiko; Oura, Yasushi

    1995-12-31

    The electropolymerized polypyrrole films formed from micellar solution of anionic surfactants, viz., Dodecylbenzene sulfonate (DBS), showed potential-dependent anion and cation ion switching behavior and the peculiar columnar structure. The formation process and the redox of the polypyrrole was studied with the in situ atomic force microscopy (AFM) and electrochemical quartz crystal microbalance (EQCM) methods. In-situ AFM observation clearly indicated that such a columnar structure started to form around critical charge densities of 60--100 mC cm{sup {minus}2}. The cyclic voltammogram for the PPy doped with DBS{sup {minus}} film showed two redox couples, each of which corresponds to a cation and an anion exchange process. Thus, the film behaves as a dual-mode ion doping/undoping exchanger. As the PPy film was prepared in higher concentration of the surfactant dopant, where the micelles are formed in solution, the resulting film showed a considerably higher (ca. three orders of magnitude) diffusion coefficient compared to ordinary PPy films so far reported. Such an enhanced diffusivity of ions could be attributed to a peculiar structure of the polymer formed. The feasibility of such polypyrrole in use of supercapacitor material was discussed.

  2. Analytical and experimental performance of a dual-mode traveling wave tube and multistage depressed collector

    NASA Technical Reports Server (NTRS)

    Ramins, Peter; Force, Dale A.; Kosmahl, Henry G.

    1987-01-01

    A computational procedure for the design of traveling-wave-tube(TWT)/refocuser/multistage depressed collector (MDC) systems was used to design a short, permanent-magnet refocusing system and a highly efficient MDC for a medium-power, dual-mode, 4.8- to 9.6-GHz TWT. The computations were carried out with advanced, multidimensional computer programs which model the electron beam and follow the trajectories of representative charges from the radiofrequency (RF) input of the TWT, through the slow-wave structure and refocusing section, to their points of impact in the depressed collector. Secondary emission losses in the MDC were treated semiquantitatively by injecting representative secondary-electron-emission current into the MDA analysis at the point of impact of each primary beam. A comparison of computed and measured TWT and MDC performance showed very good agreement. The electrodes of the MDC were fabricated from a particluar form of isptropic graphite that was selected for its low secondary electron yield, ease of machinability, and vacuum properties.

  3. Numerical Simulation of Vitiation Effects on a Hydrogen-Fueled Dual-Mode Scramjet

    NASA Technical Reports Server (NTRS)

    Vyas, Manan A.; Engblom, William A.; Georgiadis, Nicholas J.; Trefny, Charles J.; Bhagwandin, Vishal A.

    2010-01-01

    The Wind-US computational fluid dynamics (CFD) flow solver was used to simulate dual-mode direct-connect ramjet/scramjet engine flowpath tests conducted in the University of Virginia (UVa) Supersonic Combustion Facility (SCF). The objective was to develop a computational capability within Wind-US to aid current hypersonic research and provide insight to flow as well as chemistry details that are not resolved by instruments available. Computational results are compared with experimental data to validate the accuracy of the numerical modeling. These results include two fuel-off non-reacting and eight fuel-on reacting cases with different equivalence ratios, split between one set with a clean (non-vitiated) air supply and the other set with a vitiated air supply (12 percent H2O vapor). The Peters and Rogg hydrogen-air chemical kinetics model was selected for the scramjet simulations. A limited sensitivity study was done to investigate the choice of turbulence model and inviscid flux scheme and led to the selection of the k-epsilon model and Harten, Lax and van Leer (for contact waves) (HLLC) scheme for general use. Simulation results show reasonably good agreement with experimental data and the overall vitiation effects were captured.

  4. Technology Roadmap for Dual-Mode Scramjet Propulsion to Support Space-Access Vision Vehicle Development

    NASA Technical Reports Server (NTRS)

    Cockrell, Charles E., Jr.; Auslender, Aaron H.; Guy, R. Wayne; McClinton, Charles R.; Welch, Sharon S.

    2002-01-01

    Third-generation reusable launch vehicle (RLV) systems are envisioned that utilize airbreathing and combined-cycle propulsion to take advantage of potential performance benefits over conventional rocket propulsion and address goals of reducing the cost and enhancing the safety of systems to reach earth orbit. The dual-mode scramjet (DMSJ) forms the core of combined-cycle or combination-cycle propulsion systems for single-stage-to-orbit (SSTO) vehicles and provides most of the orbital ascent energy. These concepts are also relevant to two-stage-to-orbit (TSTO) systems with an airbreathing first or second stage. Foundation technology investments in scramjet propulsion are driven by the goal to develop efficient Mach 3-15 concepts with sufficient performance and operability to meet operational system goals. A brief historical review of NASA scramjet development is presented along with a summary of current technology efforts and a proposed roadmap. The technology addresses hydrogen-fueled combustor development, hypervelocity scramjets, multi-speed flowpath performance and operability, propulsion-airframe integration, and analysis and diagnostic tools.

  5. Dual modes of self-assembly in superstrongly segregated bicomponent triblock copolymer melts

    NASA Astrophysics Data System (ADS)

    Woloszczuk, Sebastian; Mineart, Kenneth P.; Spontak, Richard J.; Banaszak, Michal

    2015-01-01

    While A B C triblock copolymers are known to form a plethora of dual-mode (i.e., order-on-order) nanostructures, bicomponent A B A triblock copolymers normally self-assemble into single morphologies at thermodynamic incompatibility levels up to the strong-segregation regime. In this study, we employ on-lattice Monte Carlo simulations to examine the phase behavior of molecularly asymmetric A1B A2 copolymers possessing chemically identical endblocks differing significantly in length. In the limit of superstrong segregation, interstitial micelles composed of the minority A2 endblock are observed to arrange into two-dimensional hexagonal arrays along the midplane of B -rich lamellae in compositionally symmetric (50 :50 A :B ) copolymers. Simulations performed here establish the coupled molecular-asymmetry and incompatibility conditions under which such micelles form, as well as the temperature dependence of their aggregation number. Beyond an optimal length of the A2 endblock, the propensity for interstitial micelles to develop decreases, and the likelihood for colocation of both endblocks in the A1-rich lamellae increases. Interestingly, the strong-segregation theory of Semenov developed to explain the formation of free micelles by diblock copolymers accurately predicts the onset of interstitial micelles confined at nanoscale dimensions between parallel lamellae.

  6. A low power dual-band multi-mode RF front-end for GNSS applications

    NASA Astrophysics Data System (ADS)

    Hao, Zhang; Zhiqun, Li; Zhigong, Wang

    2010-11-01

    A CMOS dual-band multi-mode RF front-end for the global navigation satellite system receivers of all GPS, Bei-Dou, Galileo and Glonass systems is presented. It consists of a reconfigurable low noise amplifier (LNA), a broadband active balun, a high linearity mixer and a bandgap reference (BGR) circuit. The effect of the input parasitic capacitance on the input impedance of the inductively degenerated common source LNA is analyzed in detail. By using two different LC networks at the input port and the switched capacitor at the output port, the LNA can work at two different frequency bands (1.2 GHz and 1.5 GHz) under low power consumption. The active balun uses a hybrid-connection structure to achieve high bandwidth. The mixer uses the multiple gated transistors technique to acquire a high linearity under low power consumption but does not deteriorate other performances. The measurement results of the proposed front-end achieve a noise figure of 2.1/2.0 dB, again of 33.9/33.8 dB and an input 1-dB compression point of 0/1 dBm at 1227.6/1575.42 MHz. The power consumption is about 16 mW under a 1.8 V power supply.

  7. Dual-Mode SERS-Fluorescence Immunoassay Using Graphene Quantum Dot Labeling on One-Dimensional Aligned Magnetoplasmonic Nanoparticles.

    PubMed

    Zou, Fengming; Zhou, Hongjian; Tan, Tran Van; Kim, Jeonghyo; Koh, Kwangnak; Lee, Jaebeom

    2015-06-10

    A novel dual-mode immunoassay based on surface-enhanced Raman scattering (SERS) and fluorescence was designed using graphene quantum dot (GQD) labels to detect a tuberculosis (TB) antigen, CFP-10, via a newly developed sensing platform of linearly aligned magnetoplasmonic (MagPlas) nanoparticles (NPs). The GQDs were excellent bilabeling materials for simultaneous Raman scattering and photoluminescence (PL). The one-dimensional (1D) alignment of MagPlas NPs simplified the immunoassay process and enabled fast, enhanced signal transduction. With a sandwich-type immunoassay using dual-mode nanoprobes, both SERS signals and fluorescence images were recognized in a highly sensitive and selective manner with a detection limit of 0.0511 pg mL(-1). PMID:26006156

  8. Gadolinium-Induced Fibrosis.

    PubMed

    Todd, Derrick J; Kay, Jonathan

    2016-01-01

    Gadolinium-based contrast agents (GBCAs), once believed to be safe for patients with renal disease, have been strongly associated with nephrogenic systemic fibrosis (NSF), a severe systemic fibrosing disorder that predominantly afflicts individuals with advanced renal dysfunction. We provide a historical perspective on the appearance and disappearance of NSF, including its initial recognition as a discrete clinical entity, its association with GBCA exposure, and the data supporting a causative relationship between GBCA exposure and NSF. On the basis of this body of evidence, we propose that the name gadolinium-induced fibrosis (GIF) more accurately reflects the totality of knowledge regarding this disease. Use of high-risk GBCAs, such as formulated gadodiamide, should be avoided in patients with renal disease. Restriction of GBCA use in this population has almost completely eradicated new cases of this debilitating condition. Emerging antifibrotic therapies may be useful for patients who suffer from GIF. PMID:26768242

  9. Integrating Anatomic and Functional Dual-Mode Magnetic Resonance Imaging: Design and Applicability of a Bifunctional Contrast Agent.

    PubMed

    Ni, Dalong; Shen, Zhiwei; Zhang, Jiawen; Zhang, Chen; Wu, Renhua; Liu, Jianan; Yi, Meizhi; Wang, Jing; Yao, Zhenwei; Bu, Wenbo; Shi, Jianlin

    2016-03-22

    In recent decades, extensive attention has been paid to developing anatomic and functional imaging contrast agents that could provide a wealth of complementary bioimaging information. Among them, dual-mode nanoprobes that combine anatomic magnetic resonance imaging (MRI) with functional fluorescent imaging have been mostly used for separated imaging. However, the lack of a machine for simultaneous dual-mode imaging greatly limits further clinical application. One effective strategy is to rationally design MRI contrast agents that own both anatomic and functional MR imaging capability on a single MRI machine, which is highly attractive but remains a great challenge. Herein, ultrasmall NaGdF4@PLL nanodots (NDs) were developed as a novel class of MR contrast agent, which offers a high longitude relaxivity (6.42 mM(-1) s(-1)) for T1-weighted MRI and an excellent sensitive chemical exchange saturation transfer (CEST) effect for pH mapping (at +3.7 ppm). Further in vivo animal experiments show the feasibility of NaGdF4@PLL NDs as contrast agents for efficient kidney and brain tumor diagnosis and pH mapping, which will undoubtedly enhance the diagnosis accuracy and is beneficial for disease precaution and prognosis. Different from other complex dual-mode nanoprobes, the as-constructed NaGdF4@PLL NDs enable both anatomic and functional imaging on a single MR machine, which is a simple and cost-effective new approach to realize dual-mode MR imaging and holds great potential for future clinical application. PMID:26910513

  10. Effects of intermodal dispersion and fiber length on the mode-locking of a dual-core fiber laser

    NASA Astrophysics Data System (ADS)

    Fang, Xiaohui; Song, Yanrong

    2016-06-01

    We investigate theoretically how the intermodal dispersion and the fiber length influence the formation of ultrashort pulses in a dual-core fiber laser. Our simulation using the Ginzburg-Landau equation found that stable self-starting of mode-locking can be achieved with a fiber length deviating from integer multiples of the linear coupling length. Furthermore, the intermodal dispersion will not lead to pulse splitting, in contrast, it will induce asymmetry in the pulse shape and increase the modulation instability. Consequently, a filter is found necessary to stabilize the mode-locking operation when the fiber length is longer than the linear coupling length.

  11. Colorimetry and SERS dual-mode detection of telomerase activity: combining rapid screening with high sensitivity

    NASA Astrophysics Data System (ADS)

    Zong, Shenfei; Wang, Zhuyuan; Chen, Hui; Hu, Guohua; Liu, Min; Chen, Peng; Cui, Yiping

    2014-01-01

    As an important biomarker and therapeutic target, telomerase has attracted considerable attention concerning its detection and monitoring. Here, we present a colorimetry and surface enhanced Raman scattering (SERS) dual-mode telomerase activity detection method, which has several distinctive advantages. First, colorimetric functionality allows rapid preliminary discrimination of telomerase activity by the naked eye. Second, the employment of SERS technique results in greatly improved detection sensitivity. Third, the combination of colorimetry and SERS into one detection system can ensure highly efficacious and sensitive screening of numerous samples. Besides, the avoidance of polymerase chain reaction (PCR) procedures further guarantees fine reliability and simplicity. Generally, the presented method is realized by an ``elongate and capture'' procedure. To be specific, gold nanoparticles modified with Raman molecules and telomeric repeat complementary oligonucleotide are employed as the colorimetric-SERS bifunctional reporting nanotag, while magnetic nanoparticles functionalized with telomerase substrate oligonucleotide are used as the capturing substrate. Telomerase can synthesize and elongate telomeric repeats onto the capturing substrate. The elongated telomeric repeats subsequently facilitate capturing of the reporting nanotag via hybridization between telomeric repeat and its complementary strand. The captured nanotags can cause a significant difference in the color and SERS intensity of the magnetically separated sediments. Thus both the color and SERS can be used as indicators of the telomerase activity. With fast screening ability and outstanding sensitivity, we anticipate that this method would greatly promote practical application of telomerase-based early-stage cancer diagnosis.As an important biomarker and therapeutic target, telomerase has attracted considerable attention concerning its detection and monitoring. Here, we present a colorimetry and

  12. Illumination-compensated non-contact imaging photoplethysmography via dual-mode temporally coded illumination

    NASA Astrophysics Data System (ADS)

    Amelard, Robert; Scharfenberger, Christian; Wong, Alexander; Clausi, David A.

    2015-03-01

    Non-contact camera-based imaging photoplethysmography (iPPG) is useful for measuring heart rate in conditions where contact devices are problematic due to issues such as mobility, comfort, and sanitation. Existing iPPG methods analyse the light-tissue interaction of either active or passive (ambient) illumination. Many active iPPG methods assume the incident ambient light is negligible to the active illumination, resulting in high power requirements, while many passive iPPG methods assume near-constant ambient conditions. These assumptions can only be achieved in environments with controlled illumination and thus constrain the use of such devices. To increase the number of possible applications of iPPG devices, we propose a dual-mode active iPPG system that is robust to changes in ambient illumination variations. Our system uses a temporally-coded illumination sequence that is synchronized with the camera to measure both active and ambient illumination interaction for determining heart rate. By subtracting the ambient contribution, the remaining illumination data can be attributed to the controlled illuminant. Our device comprises a camera and an LED illuminant controlled by a microcontroller. The microcontroller drives the temporal code via synchronizing the frame captures and illumination time at the hardware level. By simulating changes in ambient light conditions, experimental results show our device is able to assess heart rate accurately in challenging lighting conditions. By varying the temporal code, we demonstrate the trade-off between camera frame rate and ambient light compensation for optimal blood pulse detection.

  13. Extended Constant Power Speed Range of the Brushless DC Motor Through Dual Mode Inverter Control

    SciTech Connect

    Lawler, J.S.

    2000-06-23

    The trapezoidal back electromotive force (emf) brushless direct current (dc) motor (BDCM) with surface-mounted magnets has high-power density and efficiency especially when rare-earth magnet materials are used. Traction applications, such as electric vehicles, could benefit significantly from the use of such motors. Unfortunately, a practical means for driving the motor over a constant power speed ratio (CPSR) of 5:1 or more has not yet been developed. A key feature of these motors is that they have low internal inductance. The phase advance method is effective in controlling the motor power over such a speed range, but the current at high speed may be several times greater than that required at the base speed. The increase in current during high-speed operation is due to the low motor inductance and the action of the bypass diodes of the inverter. The use of such a control would require increased current rating of the inverter semiconductors and additional cooling for the inverter, where the conduction losses increase proportionally with current, and especially for the motor, where the losses increase with the square of the current. The high current problems of phase advance can be mitigated by adding series inductance; however, this reduces power density, requires significant increase in supply voltage, and leaves the CPSR performance of the system highly sensitive to variations in the available voltage. A new inverter topology and control scheme has been developed that can drive low-inductance BDCMs over the CPSR that would be required in electric vehicle applications. This new controller is called the dual-mode inverter control (DMIC). It is shown that the BDCM has an infinite CPSR when it is driven by the DMIC.

  14. Turning performance in squid and cuttlefish: unique dual-mode, muscular hydrostatic systems.

    PubMed

    Jastrebsky, Rachel A; Bartol, Ian K; Krueger, Paul S

    2016-05-01

    Although steady swimming has received considerable attention in prior studies, unsteady swimming movements represent a larger portion of many aquatic animals' locomotive repertoire and have not been examined extensively. Squids and cuttlefishes are cephalopods with unique muscular hydrostat-driven, dual-mode propulsive systems involving paired fins and a pulsed jet. These animals exhibit a wide range of swimming behavior, but turning performance has not been examined quantitatively. Brief squid, Lolliguncula brevis, and dwarf cuttlefish, Sepia bandensis, were filmed during turns using high-speed cameras. Kinematic features were tracked, including the length-specific radius of the turn (R/L), a measure of maneuverability, and angular velocity (ω), a measure of agility. Both L. brevis and S. bandensis demonstrated high maneuverability, with (R/L)min values of 3.4×10(-3)±5.9×10(-4) and 1.2×10(-3)±4.7×10(-4) (mean±s.e.m.), respectively, which are the lowest measures of R/L reported for any aquatic taxa. Lolliguncula brevis exhibited higher agility than S. bandensis (ωa,max=725.8 versus 485.0 deg s(-1)), and both cephalopods have intermediate agility when compared with flexible-bodied and rigid-bodied nekton of similar size, reflecting their hybrid body architecture. In L. brevis, jet flows were the principal driver of angular velocity. Asymmetric fin motions played a reduced role, and arm wrapping increased turning performance to varying degrees depending on the species. This study indicates that coordination between the jet and fins is important for turning performance, with L. brevis achieving faster turns than S. bandensis and S. bandensis achieving tighter, more controlled turns than L. brevis. PMID:26944502

  15. Electromagnetic optimization of dual-mode antennas for radiometry-controlled heating of superficial tissue

    NASA Astrophysics Data System (ADS)

    Maccarini, Paolo F.; Rolfsnes, Hans O.; Neuman, Daniel G., Jr.; Johnson, Jessi E.; Juang, Titania; Jacobsen, Svein; Stauffer, Paul R.

    2005-04-01

    The large variance of survival in the treatment of large superficial tumors indicates that the efficacy of current therapies can be dramatically improved. Hyperthermia has shown significant enhancement of response when used in combination with chemotherapy and/or radiation. Control of temperature is a critical factor for treatment quality (and thus effectiveness), since the response of tumor and normal cells is significantly different over a range of just a few degrees (41-45°). For diffuse spreading tumors, microwave conformal arrays have been shown to be a sound solution to deposit the power necessary to reach the goal temperature throughout the targeted tissue. Continuous temperature monitoring is required for feedback control of power to compensate for physiologic (e.g. blood perfusion and dielectric properties) changes. Microwave radiometric thermometry has been proposed to complement individual fluoroptic probes to non-invasively map superficial and sub-surface temperatures. The challenge is to integrate the broadband antenna used for radiometric sensing with the high power antenna used for power deposition. A modified version of the dual concentric conductor antenna presented previously is optimized for such use. Several design challenges are presented including preventing unwanted radiating modes and thermal and electromagnetic coupling between the two antennas, and accommodating dielectric changes of the target tissue. Advanced 3D and planar 2D simulation software are used to achieve an initial optimized design, focused on maintaining appropriate radiation efficiency and pattern for both heating and radiometry antennas. A cutting edge automated measurement system has been realized to characterize the antennas in a tissue equivalent material and to confirm the simulation results. Finally, the guidelines for further development and improvement of this initial design are presented together with a preliminary implementation of the feedback program to be used

  16. Dual Mode Action of Mangiferin in Mouse Liver under High Fat Diet

    PubMed Central

    Lim, Jihyeon; Liu, Zhongbo; Apontes, Pasha; Feng, Daorong; Pessin, Jeffrey E.; Sauve, Anthony A.; Angeletti, Ruth H.; Chi, Yuling

    2014-01-01

    Chronic over-nutrition is a major contributor to the spread of obesity and its related metabolic disorders. Development of therapeutics has been slow compared to the speedy increase in occurrence of these metabolic disorders. We have identified a natural compound, mangiferin (MGF) (a predominant component of the plants of Anemarrhena asphodeloides and Mangifera indica), that can protect against high fat diet (HFD) induced obesity, hyperglycemia, insulin resistance and hyperlipidemia in mice. However, the molecular mechanisms whereby MGF exerts these beneficial effects are unknown. To understand MGF mechanisms of action, we performed unbiased quantitative proteomic analysis of protein profiles in liver of mice fed with HFD utilizing 15N metabolically labeled liver proteins as internal standards. We found that out of 865 quantified proteins 87 of them were significantly differentially regulated by MGF. Among those 87 proteins, 50% of them are involved in two major processes, energy metabolism and biosynthesis of metabolites. Further classification indicated that MGF increased proteins important for mitochondrial biogenesis and oxidative activity including oxoglutarate dehydrogenase E1 (Dhtkd1) and cytochrome c oxidase subunit 6B1 (Cox6b1). Conversely, MGF reduced proteins critical for lipogenesis such as fatty acid stearoyl-CoA desaturase 1 (Scd1) and acetyl-CoA carboxylase 1 (Acac1). These mass spectrometry data were confirmed and validated by western blot assays. Together, data indicate that MGF upregulates proteins pivotal for mitochondrial bioenergetics and downregulates proteins controlling de novo lipogenesis. This novel mode of dual pharmacodynamic actions enables MGF to enhance energy expenditure and inhibit lipogenesis, and thereby correct HFD induced liver steatosis and prevent adiposity. This provides a molecular basis supporting development of MGF or its metabolites into therapeutics to treat metabolic disorders. PMID:24598864

  17. M-mode echocardiograms for determination of optimal left atrial timing in patients with dual chamber pacemakers.

    PubMed

    Wish, M; Gottdiener, J S; Cohen, A I; Fletcher, R D

    1988-02-01

    To determine if the A wave of the mitral valve echocardiogram can be used as a marker for left atrial (LA) activity and assist in the programming of dual chamber pacemakers, 156 echocardiograms with the mitral A wave present were obtained from 23 patients with dual chamber pacemakers, all of whom had bipolar esophageal recordings of LA depolarization. Twelve of these patients also underwent hemodynamic study with cardiac function determined at 5 different pacemaker settings: ventricular demand pacing and dual chamber sequential pacing at 0 or 25, 150, 200 and 250 ms programming atrioventricular (AV) delay. The time delay from right atrial pacing artifact to onset and peak of mitral A wave was linearly related to the time from atrial pacing artifact to LA depolarization on the esophageal lead (p less than 0.001). As pacing mode changed from dual chamber sequential pacing (DVI) mode to atrial synchronous-ventricular pacing (VDD), the A wave came earlier relative to the ventricular pacing spike, linearly related to the LA to ventricular extension with mode change determined with the esophageal lead (r = 0.94, p less than 0.001). The time from atrial pacing to peak of A wave was shorter in patients whose optimal programmed AV delay was 150 ms compared with those whose optimal AV delay was 200 or 250 ms (p less than 0.02). At the optimal programmed delay for cardiac output, the peak of the A wave was an average of 13 +/- 36 ms after the ventricular pacing spike.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3341208

  18. High-power terahertz optical pulse generation with a dual-wavelength harmonically mode-locked Yb:YAG laser

    NASA Astrophysics Data System (ADS)

    Zhuang, W. Z.; Chang, M. T.; Su, K. W.; Huang, K. F.; Chen, Y. F.

    2013-07-01

    We report on high-power terahertz optical pulse generation with a dual-wavelength harmonically mode-locked Yb:YAG laser. A semiconductor saturable absorber mirror is developed to achieve synchronously mode-locked operation at two spectral bands centered at 1031.67 and 1049.42 nm with a pulse duration of 1.54 ps and a pulse repetition rate of 80.3 GHz. With a diamond heat spreader to improve the heat removal efficiency, the average output power can be up to 1.1 W at an absorbed pump power of 5.18 W. The autocorrelation traces reveal that the mode-locked pulse is modulated with a beat frequency of 4.92 THz and displays a modulation depth to be greater than 80%.

  19. Dual-wavelength synchronous mode-locked Yb:LSO laser using a double-walled carbon nanotube saturable absorber.

    PubMed

    Feng, Chao; Hou, Wei; Yang, Jimin; Liu, Jie; Zheng, Lihe; Su, Liangbi; Xu, Jun; Wang, Yonggang

    2016-05-01

    A dual-wavelength, passively mode-locked Yb:LSO laser was demonstrated using a double-walled carbon nanotube as a saturable absorber. The maximum average output power of the laser was 1.34 W at the incident pump power of 9.94 W. The two central wavelengths were 1057 and 1058 nm. The corresponding pulse duration of the autocorrelation interference pattern was about 15 ps, while the beat pulse repetition rate was 0.17 THz and the width of one beat pulse about 2 ps. When the incident pump power was above 10.25 W, a multiwavelength mode-locked oscillation phenomenon was observed. After employing a pair of SF10 prisms, a 1058.7 nm single-wavelength mode-locked laser was obtained with a pulse width of 7 ps. PMID:27140382

  20. Dual-mode resonant instabilities of the surface dust-acoustic wave in a Lorentzian plasma slab

    SciTech Connect

    Lee, Myoung-Jae; Jung, Young-Dae

    2015-08-15

    The dual-mode resonant instabilities of the dust-acoustic surface wave propagating at the plasma-vacuum interfaces of the generalized Lorentzian dusty plasma slab are kinetically investigated. The dispersion relation is derived for the two propagation modes: symmetric and anti-symmetric waves. We have found that the temporal growth rate of the resonant instability increases with an increase of the slab thickness for both modes. Especially, the nonthermality of plasmas enhances the growth rate of the anti-symmetric resonant wave, and the nonthermal effect is enhanced as the slab thickness is increased. It is also found that the growth rate increases with increasing angular frequency of the rotating dust grain due to the enhanced resonant energy exchange.

  1. A primer on gadolinium chemistry

    PubMed Central

    Sherry, A. Dean; Caravan, Peter; Lenkinski, Robert E.

    2010-01-01

    Gadolinium is widely known by all practitioners of MRI but few appreciate the basic solution chemistry of this trivalent lanthanide ion. Given the recent linkage between gadolinium contrast agents and nephrogenic systemic fibrosis, some basic chemistry of this ion must be more widely understood. This short primer on gadolinium chemistry is intended to provide the reader the background principles necessary to understand the basics of chelation chemistry, water hydration numbers, and the differences between thermodynamic stability and kinetic stability or inertness. We illustrate the fundamental importance of kinetic dissociation rates in determining gadolinium toxicity in vivo by presenting new data for a novel europium DOTA-tetraamide complex that is relatively unstable thermodynamically yet extraordinarily inert kinetically and also quite non-toxic. This, plus other literature evidence forms the basis of the fundamental axiom that it is the kinetic stability of a gadolinium complex, not its thermodynamic stability, that determines its in vivo toxicity. PMID:19938036

  2. Dual-mode ultrasound arrays for image-guided targeting of atheromatous plaques

    NASA Astrophysics Data System (ADS)

    Ballard, John R.; Casper, Andrew J.; Liu, Dalong; Haritonova, Alyona; Shehata, Islam A.; Troutman, Mitchell; Ebbini, Emad S.

    2012-11-01

    A feasibility study was undertaken in order to investigate alternative noninvasive treatment options for atherosclerosis. In particular, the aim of this study was to investigate the potential use of Dual-Mode Ultrasound Arrays (DMUAs) for image guided treatment of atheromatous plaques. DMUAs offer a unique treatment paradigm for image-guided surgery allowing for robust image-based identification of tissue targets for localized application of HIFU. In this study we present imaging and therapeutic results form a 3.5 MHz, 64-element fenestrated prototype DMUA for targeting lesions in the femoral artery of familial hypercholesterolemic (FH) swine. Before treatment, diagnostic ultrasound was used to verify the presence of plaque in the femoral artery of the swine. Images obtained with the DMUA and a diagnostic (HST 15-8) transducer housed in the fenestration were analyzed and used for guidance in targeting of the plaque. Discrete therapeutic shots with an estimated focal intensity of 4000-5600 W/cm2 and 500-2000 msec duration were performed at several planes in the plaque. During therapy, pulsed HIFU was interleaved with single transmit focus imaging from the DMUA and M2D imaging from the diagnostic transducer for further analysis of lesion formation. After therapy, the swine's were recovered and later sacrificed after 4 and 7 days for histological analysis of lesion formation. At sacrifice, the lower half of the swine was perfused and the femoral artery with adjoining muscle was fixed and stained with H&E to characterize HIFU-induced lesions. Histology has confirmed that localized thermal lesion formation within the plaque was achieved according to the planned lesion maps. Furthermore, the damage was confined to the plaque tissue without damage to the intima. These results offer the promise of a new treatment potentially suited for vulnerable plaques. The results also provide the first real-time demonstration of DMUA technology in targeting fine tissue structures for

  3. In Vivo application and localization of transcranial focused ultrasound using dual-mode ultrasound arrays.

    PubMed

    Haritonova, Alyona; Liu, Dalong; Ebbini, Emad S

    2015-12-01

    Focused ultrasound (FUS) has been proposed for a variety of transcranial applications, including neuromodulation, tumor ablation, and blood-brain barrier opening. A flurry of activity in recent years has generated encouraging results demonstrating its feasibility in these and other applications. To date, monitoring of FUS beams has been primarily accomplished using MR guidance, where both MR thermography and elastography have been used. The recent introduction of real-time dual-mode ultrasound array (DMUA) systems offers a new paradigm in transcranial focusing. In this paper, we present first experimental results of ultrasound-guided transcranial FUS (tFUS) application in a rodent brain, both ex vivo and in vivo. DMUA imaging is used for visualization of the treatment region for placement of the focal spot within the brain. This includes the detection and localization of pulsating blood vessels at or near the target point(s). In addition, DMUA imaging is used to monitor and localize the FUS-tissue interactions in real time. In particular, a concave (40 mm radius of curvature), 32-element, 3.5-MHz DMUA prototype was used for imaging and tFUS application in ex vivo and in vivo rat models. The ex vivo experiments were used to evaluate the point spread function of the transcranial DMUA imaging at various points within the brain. In addition, DMUA-based transcranial ultrasound thermography measurements were compared with thermocouple measurements of subtherapeutic tFUS heating in rat brain ex vivo. The ex vivo setting was also used to demonstrate the capability of DMUA to produce localized thermal lesions. The in vivo experiments were designed to demonstrate the ability of the DMUA to apply, monitor, and localize subtherapeutic tFUS patterns that could be beneficial in transient blood-brain barrier opening. The results show that although the DMUA focus is degraded due to the propagation through the skull, it still produces localized heating effects within a sub

  4. In Vivo Application and Localization of Transcranial Focused Ultrasound Using Dual-Mode Ultrasound Arrays

    PubMed Central

    Haritonova, Alyona; Liu, Dalong; Ebbini, Emad S.

    2015-01-01

    Focused ultrasound (FUS) has been proposed for a variety of transcranial applications, including neuromodulation, tumor ablation, and blood brain barrier opening. A flurry of activity in recent years has generated encouraging results demonstrating its feasibility in these and other applications. To date, monitoring of FUS beams have been primarily accomplished using MR guidance, where both MR thermography and elastography have been used. The recent introduction of real-time dual-mode ultrasound array (DMUA) systems offers a new paradigm in transcranial focusing. In this paper, we present first experimental results of ultrasound-guided transcranial FUS (tFUS) application in a rodent brain, both ex vivo and in vivo. DMUA imaging is used for visualization of the treatment region for placement of the focal spot within the brain. This includes the detection and localization of pulsating blood vessels at or near the target point(s). In addition, DMUA imaging is used to monitor and localize the FUS-tissue interactions in real-time. In particular, a concave (40-mm radius of curvature), 32-element, 3.5 MHz DMUA prototype was used for imaging and tFUS application in ex vivo and in vivo rat model. The ex vivo experiments were used to evaluate the point spread function (psf) of the transcranial DMUA imaging at various points within the brain. In addition, DMUA-based transcranial ultrasound thermography measurements were compared with thermocouple measurements of subtherapeutic tFUS heating in rat brain ex vivo. The ex vivo setting was also used to demonstrate the DMUA capability to produce localized thermal lesions. The in vivo experiments were designed to demonstrate the ability of the DMUA to apply, monitor, and localize subtherapeutic tFUS patterns that could be beneficial in transient blood brain barrier opening. The results show that, while the DMUA focus is degraded due to the propagation through the skull, it still produces localized heating effects within sub

  5. Polarization and propagation characteristics of switchable first-order azimuthally asymmetric beam generated in dual-mode fiber.

    PubMed

    Khan, Saba N; Chatterjee, Sudip K; Chaudhuri, Partha Roy

    2015-02-20

    We report here the controlled generation of a linearly polarized first-order azimuthally asymmetric beam (F-AAB) in a dual-mode fiber (DMF) by appropriate superposition of selectively excited zeroth-order vector modes that are doughnut-shaped azimuthally symmetric beams (D-ASBs). We first demonstrate continually switching polarization mode structures having an identical two-lobe intensity profile (i.e., intra-F-AAB conversion). Then, under a distinct launching state, we generate mode structures progressively toggling between the doughnut-shaped profile and two-lobe pattern having dissimilar polarization orientations (i.e., F-AAB to D-ASB conversion). Interestingly, a decentralized elliptical Gaussian beam possessing homogenous spatial polarization is obtained by enhancing the contribution of the fundamental mode (HE11/LP01) in selectively excited F-AAB. A smoothly varying azimuth of the input beam in this situation resulted in redistribution of transverse energy procuring a unique and exciting unconventional two-grain T-polarized beam having mutually orthogonal state of polarization (SOP). All of the above three were achieved under a given set of launching conditions (tilt/offset) of a Gaussian mode (TEM00) devised with changing SOP of the input beam. A strong modulation in the output beam characteristics was also observed with the variation in propagation distance (for a fixed input SOP) owing to the large difference in propagation constants of the participating modes (LP01 and one of the F-AABs). Finally, this particular study led to a design for a low-cost highly sensitive strain measuring device based on tracking the centroid movement of the output intensity pattern. Each of our experimentally observed intensity/polarization distributions is theoretically mapped on a one-to-one basis considering a linear superposition of appropriately excited LP basis modes of the waveguide toward a complete understanding of the

  6. Decentralized Sliding Mode Observer Based Dual Closed-Loop Fault Tolerant Control for Reconfigurable Manipulator against Actuator Failure.

    PubMed

    Zhao, Bo; Li, Chenghao; Liu, Derong; Li, Yuanchun

    2015-01-01

    This paper considers a decentralized fault tolerant control (DFTC) scheme for reconfigurable manipulators. With the appearance of norm-bounded failure, a dual closed-loop trajectory tracking control algorithm is proposed on the basis of the Lyapunov stability theory. Characterized by the modularization property, the actuator failure is estimated by the proposed decentralized sliding mode observer (DSMO). Moreover, the actuator failure can be treated in view of the local joint information, so its control performance degradation is independent of other normal joints. In addition, the presented DFTC scheme is significantly simplified in terms of the structure of the controller due to its dual closed-loop architecture, and its feasibility is highly reflected in the control of reconfigurable manipulators. Finally, the effectiveness of the proposed DFTC scheme is demonstrated using simulations. PMID:26181826

  7. Decentralized Sliding Mode Observer Based Dual Closed-Loop Fault Tolerant Control for Reconfigurable Manipulator against Actuator Failure

    PubMed Central

    Zhao, Bo; Li, Yuanchun

    2015-01-01

    This paper considers a decentralized fault tolerant control (DFTC) scheme for reconfigurable manipulators. With the appearance of norm-bounded failure, a dual closed-loop trajectory tracking control algorithm is proposed on the basis of the Lyapunov stability theory. Characterized by the modularization property, the actuator failure is estimated by the proposed decentralized sliding mode observer (DSMO). Moreover, the actuator failure can be treated in view of the local joint information, so its control performance degradation is independent of other normal joints. In addition, the presented DFTC scheme is significantly simplified in terms of the structure of the controller due to its dual closed-loop architecture, and its feasibility is highly reflected in the control of reconfigurable manipulators. Finally, the effectiveness of the proposed DFTC scheme is demonstrated using simulations. PMID:26181826

  8. High-frequency dual mode pulsed wave Doppler imaging for monitoring the functional regeneration of adult zebrafish hearts

    PubMed Central

    Kang, Bong Jin; Park, Jinhyoung; Kim, Jieun; Kim, Hyung Ham; Lee, Changyang; Hwang, Jae Youn; Lien, Ching-Ling; Shung, K. Kirk

    2015-01-01

    Adult zebrafish is a well-known small animal model for studying heart regeneration. Although the regeneration of scars made by resecting the ventricular apex has been visualized with histological methods, there is no adequate imaging tool for tracking the functional recovery of the damaged heart. For this reason, high-frequency Doppler echocardiography using dual mode pulsed wave Doppler, which provides both tissue Doppler (TD) and Doppler flow in a same cardiac cycle, is developed with a 30 MHz high-frequency array ultrasound imaging system. Phantom studies show that the Doppler flow mode of the dual mode is capable of measuring the flow velocity from 0.1 to 15 cm s−1 with high accuracy (p-value = 0.974 > 0.05). In the in vivo study of zebrafish, both TD and Doppler flow signals were simultaneously obtained from the zebrafish heart for the first time, and the synchronized valve motions with the blood flow signals were identified. In the longitudinal study on the zebrafish heart regeneration, the parameters for diagnosing the diastolic dysfunction, for example, E/Em < 10, E/A < 0.14 for wild-type zebrafish, were measured, and the type of diastolic dysfunction caused by the amputation was found to be similar to the restrictive filling. The diastolic function was fully recovered within four weeks post-amputation. PMID:25505135

  9. A Dual-Mode Bandpass Filter with Multiple Controllable Transmission-Zeros Using T-Shaped Stub-Loaded Resonators

    PubMed Central

    Yao, Zh.; Wang, C.; Kim, N. Y.

    2014-01-01

    A dual-mode broadband bandpass filter (BPF) with multiple controllable transmission-zeros using T-shaped stub-loaded resonators (TSSLRs) is presented. Due to the symmetrical plane, the odd-even-mode theory can be adopted to characterize the BPF. The proposed filter consists of a dual-mode TSSLR and two modified feed-lines, which introduce two capacitive and inductive source-load (S-L) couplings. Five controllable transmission zeros (TZs) can be achieved for the high selectivity and the wide stopband because of the tunable amount of coupling capacitance and inductance. The center frequency of the proposed BPF is 5.8 GHz, with a 3 dB fraction bandwidth of 8.9%. The measured insertion and return losses are 1.75 and 28.18 dB, respectively. A compact size and second harmonic frequency suppression can be obtained by the proposed BPF with S-L couplings. PMID:24688406

  10. Tunable photonic microwave notch filter using SOA-based single-longitudinal mode, dual-wavelength laser.

    PubMed

    Lee, Kwanil; Lee, Ju Han; Lee, Sang Bae

    2009-07-20

    A novel photonic microwave notch filter with capability of frequency tuning is proposed and experimentally demonstrated. The scheme is based on a fiber Bragg grating (FBG)-based, single longitudinal mode, wavelength-spacing tunable dual-wavelength fiber laser and a dispersive fiber delay line. By using a symmetrical S-bending technique along the FBGs, the wavelength spacing of the laser can be tuned, which enables the microwave notch frequency tuning. Experimental results show that the notch rejection of more than 30 dB and the flexible tunability of notch frequency can be readily achieved in the range of 1.2 approximately 6.7 GHz. PMID:19654727

  11. Heating mode transition in a hybrid direct current/dual-frequency capacitively coupled CF{sub 4} discharge

    SciTech Connect

    Zhang, Quan-Zhi; Wang, You-Nian; Bogaerts, Annemie

    2014-06-14

    Computer simulations based on the particle-in-cell/Monte Carlo collision method are performed to study the plasma characteristics and especially the transition in electron heating mechanisms in a hybrid direct current (dc)/dual-frequency (DF) capacitively coupled CF{sub 4} discharge. When applying a superposed dc voltage, the plasma density first increases, then decreases, and finally increases again, which is in good agreement with experiments. This trend can be explained by the transition between the four main heating modes, i.e., DF coupling, dc and DF coupling, dc source dominant heating, and secondary electron dominant heating.

  12. Electron heating mode transition induced by mixing radio frequency and ultrahigh frequency dual frequency powers in capacitive discharges

    NASA Astrophysics Data System (ADS)

    Sahu, B. B.; Han, Jeon G.

    2016-05-01

    Electron heating mode transitions induced by mixing the low- and high-frequency power in dual-frequency nitrogen discharges at 400 mTorr pressure are presented. As the low-frequency (13.56 MHz) power decreases and high-frequency (320 MHz) power increases for the fixed power of 200 W, there is a transition of electron energy distribution function (EEDF) from Druyvesteyn to bi-Maxwellian type characterized by a distinguished warm electron population. It is shown that this EEDF evolution is attributed to the transition from collisional to collisionless stochastic heating of the low-energy electrons.

  13. Dual-mode super-resolution imaging with stimulated emission depletion microscopy and fluorescence emission difference microscopy.

    PubMed

    Wang, Yifan; Ma, Ye; Kuang, Cuifang; Fang, Yue; Xu, Yingke; Liu, Xu; Ding, Zhihua

    2015-06-10

    Dual-mode super-resolution imaging system with two different super-resolution imaging methods, STED and FED, is presented. Electrical shutters controlled by the host computer are introduced to switch the two imaging modes. Principles of both methods are analyzed theoretically, and enhancements in the lateral resolution and SNR are demonstrated theoretically and experimentally. Results show that both imaging methods offered by the proposed system can break the diffraction barrier. Furthermore, the presented system provides a meaningful way to image fluorescent samples by a corresponding imaging mode according to the specific characteristics of samples analyzed for study. For samples that can endure high-power illumination, it is appropriate to use the STED mode to achieve a better resolution, while for samples that are vulnerable to high intensity, the FED method is a better choice because no high-power beam is needed, and the FED method can provide better resolution than STED when no high-power beam is allowed. The flexible switching of the two super-resolution imaging modes can help researchers to make most of the advantages of each imaging method. It is believed that the presented system has the potential to be widely used in future nanoscale investigations. PMID:26192843

  14. Analysis of temperature and strain sensitivity of fiber Bragg gratings written in dual-mode highly birefringent microstructured fibers

    NASA Astrophysics Data System (ADS)

    Tenderenda, T.; Murawski, M.; Szymanski, M.; Becker, M.; Rothhardt, M.; Bartelt, H.; Mergo, P.; Poturaj, K.; Makara, M.; Skorupski, K.; Marc, P.; Jaroszewicz, L. R.; Nasilowski, T.

    2013-05-01

    Fiber Bragg gratings (FBG) are one of the most successful fiber optic technologies with very interesting perspectives for application in fiber optic sensing. It has been already reported that the possibility of its fabrication in novel microstructured fibers (MSF), creating a unique 3D structure, can significantly improve their performance and sensing properties. In this paper we present the results of FBG inscription in a dual-mode highly birefringent (HB) MSF with enhanced polarimetric strain sensitivity of the second order mode, as its mode maxima are closer to the cladding air-holes, where the strain distribution during fiber elongation is the highest. We perform an analysis and comparison of the FBG reflection and transmission characteristics, showing the effects of power coupling to cladding radiation modes. Furthermore we present the results of temperature and longitudinal strain sensitivities of the particular modes visible in the grating reflection spectrum followed by conclusions with reference to our previously reported results of polarimetric strain and temperature measurements of a similar fiber design.

  15. Shear Fracture of Dual Phase AHSS in the Process of Stamping: Macroscopic Failure Mode and Micro-level Metallographical Observation

    NASA Astrophysics Data System (ADS)

    Wang, Wurong; Wei, Xicheng; Yang, Jun; Shi, Gang

    2011-08-01

    Due to its excellent strength and formability combinations, dual phase (DP) steels offer the potential to improve the vehicle crashworthiness performance without increasing car body weight and have been increasingly used into new vehicles. However, a new type of crack mode termed as shear fracture is accompanied with the application of these high strength DP steel sheets. With the cup drawing experiment to identify the limit drawing ratio (LDR) of three DP AHSS with strength level from 600 MPa to 1000 MPa, the study compared and categorized the macroscopic failure mode of these three types of materials. The metallographical observation along the direction of crack was conducted for the DP steels to discover the micro-level propagation mechanism of the fracture.

  16. Dual-wavelength asynchronous and synchronous mode-locking operation by a Nd:CLTGG disordered crystal

    NASA Astrophysics Data System (ADS)

    Xu, J.-L.; Guo, S.-Y.; He, J.-L.; Zhang, B.-Y.; Yang, Y.; Yang, H.; Liu, S.-D.

    2012-04-01

    We have developed a diode-pumped passively mode-locked Nd3+:CLTGG laser operated at 1059 and 1061 nm with a semiconductor saturable absorber mirror (SESAM). The relative intensity of the two spectrum wavelengths is adjustable, allowing asynchronous and synchronous generation of the dual-wavelength pulses. In synchronous mode-locking regime, a total average output power of 383 mW was obtained with pulse duration of 3.5 ps and repetition rate of 42 MHz. The two spectral bands of 1059 and 1061 nm had the same intensities and areas, indicating 1:1 for the pulse energy ratio. It is desirable for efficiently generating a terahertz wave by difference-frequency generation.

  17. Stable dual-wavelength single-longitudinal-mode ring erbium-doped fiber laser for optical generation of microwave frequency

    NASA Astrophysics Data System (ADS)

    Wang, T.; Liang, G.; Miao, X.; Zhou, X.; Li, Q.

    2012-05-01

    We demonstrate a simple dual-wavelength ring erbium-doped fiber laser operating in single-longitudinal-mode (SLM) at room temperature. A pair of reflection type short-period fiber Bragg gratings (FBGs), which have two different center wavelengths of 1545.072 and 1545.284 nm, are used as the wavelength-selective component of the laser. A segment of unpumped polarization maintaining erbium-doped fiber (PM-EDF) is acted as a narrow multiband filter. By turning the polarization controller (PC) to enhance the polarization hole burning (PHB), the single-wavelength and dual-wavelength laser oscillations are observed at 1545.072 and 1545.284 nm. The output power variation is less than 0.6 dB for both wavelengths over a five-minute period and the optical signal to noise ratio (OSNR) is greater than 50 dB. By beating the dual-wavelengths at a photodetector (PD), a microwave signal at 26.44 GHz is demonstrated.

  18. Thermodynamic modeling of protein retention in mixed-mode chromatography: An extended model for isocratic and dual gradient elution chromatography.

    PubMed

    Lee, Yi Feng; Graalfs, Heiner; Frech, Christian

    2016-09-16

    An extended model is developed to describe protein retention in mixed-mode chromatography based on thermodynamic principles. Special features are the incorporation of pH dependence of the ionic interaction on a mixed-mode resin and the addition of a water term into the model which enables one to describe the total number of water molecules released at the hydrophobic interfaces upon protein-ligand binding. Examples are presented on how to determine the model parameters using isocratic elution chromatography. Four mixed-mode anion-exchanger prototype resins with different surface chemistries and ligand densities were tested using isocratic elution of two monoclonal antibodies at different pH values (7-10) and encompassed a wide range of NaCl concentrations (0-5M). U-shape mixed-mode retention curves were observed for all four resins. By taking into account of the deprotonation and protonation of the weak cationic functional groups in these mixed-mode anion-exchanger prototype resins, conditions which favor protein-ligand binding via mixed-mode strong cationic ligands as well as conditions which favor protein-ligand binding via both mixed-mode strong cationic ligands and non-hydrophobic weak cationic ligands were identified. The changes in the retention curves with pH, salt, protein, and ligand can be described very well by the extended model using meaningful thermodynamic parameters like Gibbs energy, number of ionic and hydrophobic interactions, total number of released water molecules as well as modulator interaction constant. Furthermore, the fitted model parameters based on isocratic elution data can also be used to predict protein retention in dual salt-pH gradient elution chromatography. PMID:27554024

  19. A new designed dual-guided ring-core fiber for OAM mode transmission

    NASA Astrophysics Data System (ADS)

    Zhu, Min; Zhang, Wenbo; Xi, Lixia; Tang, Xianfeng; Zhang, Xiaoguang

    2015-10-01

    We propose and analyze a design of multi-OAM-modes ring-core fiber with two guided modes regions which possess relatively large effective index separations required for the vector modes transmission. The proposed fiber can support up to 28 information states bearing OAM spanning 8 OAM orders in the ring region, and two degenerate fundamental polarization modes in the core region across the whole C bands. Fiber features such as dispersion, differential mode delay, effective mode area, power isolation between two guided regions and modal birefringence have been analyzed in this paper. For the reason that the proposed fiber possess the relatively good features, it has potential applications in the next generation fiber communication systems either in the quantum domain or in the classical domain.

  20. A dual-mode signaling response of a AuNP-fluorescein based probe for specific detection of thiourea.

    PubMed

    Chen, Chuanxia; Zhao, Dan; Sun, Jian; Yang, Xiurong

    2016-04-21

    By employing fluorescein and AuNPs as energy donors and acceptors, respectively, a novel fluorescence resonance energy transfer (FRET)-based dual-mode sensor for selective recognition and quantitative detection of thiourea was designed and constructed in this study for the first time. Herein, it is demonstrated that fluorescein could be adsorbed on the surface of AuNPs and induce fluorescence quenching through the well-known FRET process. The preferential introduction of thiourea would reduce the overall surface negative charges of AuNPs by replacing the original citrate groups, leading to the aggregation of AuNPs. Meanwhile, thiourea could prevent the binding between fluorescein and AuNPs, reduce the as-formed FRET effect, and then lead to fluorescence recovery of the fluorescein. Therefore, a dual-mode sensor with AuNP-related colorimetric and fluorescein-based fluorescence readout was rationally developed. Under the optimum conditions, the detection limits were calculated to be 10 nM and 23 nM for fluorescent and colorimetric sensors, individually, and a limit of 0.4 μM was detected by the naked eye. Finally, such a simple, convenient, cost-effective, highly selective and sensitive sensing assay was successfully applied in the detection of thiourea in tap water and fruit juice samples. PMID:27031921

  1. Terminalia Chebula provides protection against dual modes of necroptotic and apoptotic cell death upon death receptor ligation.

    PubMed

    Lee, Yoonjung; Byun, Hee Sun; Seok, Jeong Ho; Park, Kyeong Ah; Won, Minho; Seo, Wonhyoung; Lee, So-Ra; Kang, Kidong; Sohn, Kyung-Cheol; Lee, Ill Young; Kim, Hyeong-Geug; Son, Chang Gue; Shen, Han-Ming; Hur, Gang Min

    2016-01-01

    Death receptor (DR) ligation elicits two different modes of cell death (necroptosis and apoptosis) depending on the cellular context. By screening a plant extract library from cells undergoing necroptosis or apoptosis, we identified a water extract of Terminalia chebula (WETC) as a novel and potent dual inhibitor of DR-mediated cell death. Investigation of the underlying mechanisms of its anti-necroptotic and anti-apoptotic action revealed that WETC or its constituents (e.g., gallic acid) protected against tumor necrosis factor-induced necroptosis via the suppression of TNF-induced ROS without affecting the upstream signaling events. Surprisingly, WETC also provided protection against DR-mediated apoptosis by inhibition of the caspase cascade. Furthermore, it activated the autophagy pathway via suppression of mTOR. Of the WETC constituents, punicalagin and geraniin appeared to possess the most potent anti-apoptotic and autophagy activation effect. Importantly, blockage of autophagy with pharmacological inhibitors or genetic silencing of Atg5 selectively abolished the anti-apoptotic function of WETC. These results suggest that WETC protects against dual modes of cell death upon DR ligation. Therefore, WETC might serve as a potential treatment for diseases characterized by aberrantly sensitized apoptotic or non-apoptotic signaling cascades. PMID:27117478

  2. Terminalia Chebula provides protection against dual modes of necroptotic and apoptotic cell death upon death receptor ligation

    PubMed Central

    Lee, Yoonjung; Byun, Hee Sun; Seok, Jeong Ho; Park, Kyeong Ah; Won, Minho; Seo, Wonhyoung; Lee, So-Ra; Kang, Kidong; Sohn, Kyung-Cheol; Lee, Ill Young; Kim, Hyeong-Geug; Son, Chang Gue; Shen, Han-Ming; Hur, Gang Min

    2016-01-01

    Death receptor (DR) ligation elicits two different modes of cell death (necroptosis and apoptosis) depending on the cellular context. By screening a plant extract library from cells undergoing necroptosis or apoptosis, we identified a water extract of Terminalia chebula (WETC) as a novel and potent dual inhibitor of DR-mediated cell death. Investigation of the underlying mechanisms of its anti-necroptotic and anti-apoptotic action revealed that WETC or its constituents (e.g., gallic acid) protected against tumor necrosis factor-induced necroptosis via the suppression of TNF-induced ROS without affecting the upstream signaling events. Surprisingly, WETC also provided protection against DR-mediated apoptosis by inhibition of the caspase cascade. Furthermore, it activated the autophagy pathway via suppression of mTOR. Of the WETC constituents, punicalagin and geraniin appeared to possess the most potent anti-apoptotic and autophagy activation effect. Importantly, blockage of autophagy with pharmacological inhibitors or genetic silencing of Atg5 selectively abolished the anti-apoptotic function of WETC. These results suggest that WETC protects against dual modes of cell death upon DR ligation. Therefore, WETC might serve as a potential treatment for diseases characterized by aberrantly sensitized apoptotic or non-apoptotic signaling cascades. PMID:27117478

  3. A Multifunctional Theranostic Nanoagent for Dual-Mode Image-Guided HIFU/Chemo- Synergistic Cancer Therapy

    PubMed Central

    Zhang, Nan; Cai, Xiaojun; Gao, Wei; Wang, Ronghui; Xu, Chunyan; Yao, Yuanzhi; Hao, Lan; Sheng, Danli; Chen, Hangrong; Wang, Zhigang; Zheng, Yuanyi

    2016-01-01

    High-intensity focused ultrasound (HIFU) is deemed to be a promising noninvasive therapeutic modality for cancers as well as non-neoplastic diseases. However, the accuracy of the technique in the diagnosis and treatment of tumors remains unsatisfactory. HIFU, when combined with multifunctional synergistic agents (SAs), has the potential to be of greater diagnostic and therapeutic efficacy. Here we describe a smart and multifunctional hollow mesoporous Prussian blue (HMPBs) theranostic nanoplatform, the hollow structure of which is capable of encapsulating doxorubicin (DOX) and perfluorohexane (HMPBs-DOX/PFH). In vitro and in vivo studies validated that HMPBs-DOX/PFH can be used as an amplifiable dual-mode imaging contrast agent, which can simultaneously enhance ultrasound (US) and photoacoustic (PA) imaging for guiding and monitoring tumor therapy. When exposed to HIFU, this versatile HMPBs-DOX/PFH agent could increase the cavitation effect and use lower HIFU intensity to achieve coagulative necrosis. Furthermore, it significantly accelerated the release of DOX thereby enhancing chemotherapeutic efficacy and avoiding systemic side effects of the drug. Such a novel theranostic nanoplatform is expected to integrate dual-mode guided imaging with greater therapeutic efficacy and fewer side effects and is very promising for the noninvasive synergistic tumor therapy. PMID:26909114

  4. Dual-Mode Encoded Magnetic Composite Microsphere Based on Fluorescence Reporters and Raman Probes as Covert Tag for Anticounterfeiting Applications.

    PubMed

    Li, Ruimin; Zhang, Yuting; Tan, Jing; Wan, Jiaxun; Guo, Jia; Wang, Changchun

    2016-04-13

    Utilizing fluorescence reporters and SERS probes as the security labels, a series of dual-mode encoded magnetic composite microspheres with micrometer size was designed and prepared for anticounterfeiting applications. At first, the micro-meter-sized melamine formaldehyde microspheres with different fluorescence molecules (FMF) were prepared by precipitation polymerization, and then the magnetite composite microspheres (FMF/MNPs) were fabricated by direct immobilization of magnetic nanoparticles (MNPs) onto the surface of FMF microspheres. After deposition of Ag nanoparticles (Ag-NPs) onto FMF/MNPs microspheres, the SERS probes were absorbed onto the surface of Ag-NPs, and then a protection layer of silica was coated on the composite microspheres by Stöber method. The combination of different fluorescence reporters and SERS probes greatly increased the encoding complexity and volume for high-level anticounterfeiting. The structure of the dual-encoded FMF/MNPs/Ag-NPs/SiO2 composite microspheres was characterized by FESEM, TEM, FLS(fluorescence spectrometer), XRD, VSM, UV-vis and EDS. The embedded magnetic nanoparticles enable the composite microspheres to be quickly isolated from the marked latex paint by magnet at the concentration of as low as 1 ppm, and the covert tag information can be read out even from one composite microsphere. In addition, the covert security information in the marked coating film can be also read out in situ and the existence of the composite microspheres does not influence the visible appearance of the coating film. All the above outstanding properties will make these dual-mode encoded composite microspheres as advanced security tags for next-generation anticounterfeiting applications. PMID:27010437

  5. In-fiber liquid-level probe based on Michelson interferometer via dual-mode elliptical multilayer-core fiber

    NASA Astrophysics Data System (ADS)

    Liang, Xiao; Ren, Guobin; Li, Yang; Liu, Zhibo; Wei, Huai; Jian, Shuisheng

    2016-07-01

    An in-fiber liquid-level probe fabricated from homemade dual-mode elliptical multilayer-core fiber (EMCF) was proposed and experimentally demonstrated. The proposed sensor simply consists of a segment of the EMCF with one end coated with silver film, and a Michelson interferometer is roughly established when light from single-mode fiber incident from the other end. The detected interference patterns, rather clean due to the few-mode property, shift as the liquid level due to strong interaction between high-order modes and measurands through evanescent waves. Both the propagation characteristics and operation principle of such a sensor were demonstrated in detail, and sensitivities of 33.48, 43.35, and 48.93 pm/mm corresponding to liquid indices of 1.333, 1.353, and 1.373 were successfully achieved with a 50-mm EMCF probe, respectively. Moreover, the proposed sensor had the potential to discriminate measurand index after proper calibration.

  6. In vivo evaluation of a mechanically oscillating dual-mode applicator for ultrasound imaging and thermal ablation.

    PubMed

    Owen, Neil R; Bouchoux, Guillaume; Seket, Belhassen; Murillo-Rincon, Adriana; Merouche, Samir; Birer, Alain; Paquet, Christian; Delabrousse, Eric; Chapelon, Jean-Yves; Berriet, Rémi; Fleury, Gérard; Lafon, Cyril

    2010-01-01

    Unresectable liver tumors are often treated with interstitial probes that modify tissue temperature, and efficacious treatment relies on image guidance for tissue targeting and assessment. Here, we report the in vivo evaluation of an interstitial applicator with a mechanically oscillating five-element dual-mode transducer. After thoroughly characterizing the transducer, tissue response to high-intensity ultrasound was numerically calculated to select parameters for experimentation in vivo. Using perfused porcine liver, B-mode sector images were formed before and after a 120-s therapy period, and M-mode imaging monitored the therapy axis during therapy. The time-averaged transducer surface intensity was 21 or 27 W/cm (2). Electroacoustic conversion efficiency was maximally 72 +/- 3% and impulse response length was 295 +/- 1.0 ns at -6 dB. The depth of thermal damage measured by gross histology ranged from 10 to 25 mm for 13 insertion sites. For six sites, M-mode data exhibited a reduction in gray-scale intensity that was interpreted as the temporal variation of coagulation necrosis. Contrast ratio analysis indicated that the gray-scale intensity dropped by 7.8 +/- 3.3 dB, and estimated the final lesion depth to an accuracy of 2.3 +/- 2.4 mm. This paper verified that the applicator could induce coagulation necrosis in perfused liver and demonstrated the feasibility of real-time monitoring. PMID:19497808

  7. Temporal mode sorting using dual-stage quantum frequency conversion by asymmetric Bragg scattering.

    PubMed

    Christensen, Jesper B; Reddy, Dileep V; McKinstrie, C J; Rottwitt, K; Raymer, M G

    2015-09-01

    The temporal shape of single photons provides a high-dimensional basis of temporal modes, and can therefore support quantum computing schemes that go beyond the qubit. However, the lack of linear optical components to act as quantum gates has made it challenging to efficiently address specific temporal-mode components from an arbitrary superposition. Recent progress towards realizing such a "quantum pulse gate," has been proposed using nonlinear optical signal processing to add coherently the effect of multiple stages of quantum frequency conversion. This scheme, called temporal-mode interferometry [D. V. Reddy, Phys. Rev. A 91, 012323 (2015)], has been shown in the case of three-wave mixing to promise near-unity mode-sorting efficiency. Here we demonstrate that it is also possible to achieve high mode-sorting efficiency using four-wave mixing, if one pump pulse is long and the other short - a configuration we call asymmetrically-pumped Bragg scattering. PMID:26368430

  8. Multistage depressed collector with efficiency of 90 to 94 percent for operation of a dual-mode traveling wave tube in the linear region

    NASA Technical Reports Server (NTRS)

    Ramins, P.; Fox, T. A.

    1980-01-01

    An axisymmetric, multistage, depressed collector of fixed geometric design was evaluated in conjunction with an octave bandwidth, dual mode traveling wave tube (TWT). The TWT was operated over a wide range of conditions to simulate different applications. The collector performance was optimized (within the constraint of fixed geometric design) over the range of TWT operating conditions covered. For operation of the TWT in the linear, low distortion range, 90 percent and greater collector efficiencies were obtained leading to TWT overall efficiencies of 20 to 35 percent, as compared with 2 to 5 percent with an undepressed collector. With collectors of this efficiency and minimized beam interception losses, it becomes practical to design dual mode TWT's such that the low mode can represent operation well below saturation. Consequently, the required pulse up in beam current can be reduced or eliminated, and this mitigates beam control and dual mode TWT circuit design problems. For operation of the dual mode TWT at saturation, average collector efficiencies in excess of 85 percent were obtained for both the low and high modes across an octave bandwidth, leading to a three to fourfold increase in the TWT overall efficiency.

  9. Selectable dual-wavelength erbium-doped fiber laser with stable single-longitudinal-mode utilizing eye-type compound-ring configuration

    NASA Astrophysics Data System (ADS)

    Yeh, Chien-Hung; Chen, Jhih-Yu; Chen, Hone-Zhang; Chow, Chi-Wai

    2016-08-01

    In this paper, a tunable dual-wavelength erbium-doped fiber (EDF) ring laser with stable single-longitudinal-mode (SLM) under a tuning range of 1530.0-1560.0 nm is proposed and demonstrated. Here, the mode spacing of lasing dual-wavelength from 1.0 to 30.0 nm can be selected arbitrarily in any wavelength position. To accomplish the SLM output, the eye-type compound-ring scheme is proposed inside ring cavity for suppressing the multi-longitudinal-mode (MLM) highly. The entire measured output power and optical signal to noise ratio (OSNR) of each dual-wavelength are larger than -13.3 dBm and 60 dB respectively. In addition, the output stability measurement of proposed EDF laser is also performed and analyzed.

  10. Stabilized dual-wavelength erbium-doped fiber laser with a single-longitudinal mode by utilizing fiber Bragg grating and a compound-ring filter

    NASA Astrophysics Data System (ADS)

    Yeh, Chien-Hung; Chen, Hone-Zhang; Chen, Jhih-Yu; Chow, Chi-Wai

    2016-02-01

    In this investigation, a stable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber (EDF) multiring laser by utilizing fiber Bragg grating is proposed and investigated. Here, to accomplish a SLM output, the multiring cavity of the proposed EDF laser is employed for suppressing the densely multilongitudinal mode. Hence, the output powers and wavelengths of the proposed dual-wavelength EDF laser are 7.0 and 6.7 dBm and 1531.72 and 1537.32 nm, respectively. In addition, the maximum output stabilities of the power and wavelength in the proposed laser are also executed and discussed.

  11. Laserspektroskopie Gadoliniums Fingerabdruck

    SciTech Connect

    Blaum, Klaus; Bushaw, Bruce A.; Nortershauser, Wilfried

    2003-05-31

    The minimum energy that is required to remove the first electron from e neutral atom, one call ionization energy E1. It is not only for every element of the periodic table but also even for every nuclide characteristic and therefore belongs to the most basic atomic properties. The ionization energy is important for the determination of a ‘row’ of properties, from the chemical reactivity to the color light absorbed and emitted from an atom. The value of E1 depends on the stationary state that the farthest electron originally occupies. If the electron finds itself, however, in the first excited stat, only 3.4 eV is required. Previously the ionization energy could be determined with high accuracy in the range of 10-8 by means of laser spectroscopy only for atoms with one or two valence electrons, whereby the most accurate to date result from measurements on Hydrogen. We could now, for the first time in a rare earth element, reach that kind of accuracy. Motivation for these investigations was the development of an analysis method for the ultra-trace detection of Gadolinium in tissue- and meteorite samples.

  12. Dual-mode on-demand droplet routing in multiple microchannels using a magnetic fluid as carrier phase

    PubMed Central

    Kim, Jitae; Won, June; Song, Simon

    2014-01-01

    We present dual-mode, on-demand droplet routing in a multiple-outlet microfluidic device using an oil-based magnetic fluid. Magnetite (Fe3O4) nanoparticle-contained oleic acid (MNOA) was used as a carrier phase for droplet generation and manipulation. The water-in-MNOA droplets were selectively distributed in a curved microchannel with three branches by utilizing both a hydrodynamic laminar flow pattern and an external magnetic field. Without the applied magnetic field, the droplets travelled along a hydrodynamic centerline that was displaced at each bifurcating junction. However, in the presence of a permanent magnet, they were repelled from the centerline and diverted into the desired channel when the repelled distance exceeded the minimum offset allocated to the channel. The repelled distance, which is proportional to the magnetic field gradient, was manipulated by controlling the magnet's distance from the device. To evaluate routing performance, three different sizes of droplets with diameters of 63, 88, and 102 μm were directed into designated outlets with the magnet positioned at varying distances. The result demonstrated that the 102-μm droplets were sorted with an accuracy of ∼93%. Our technique enables on-demand droplet routing in multiple outlet channels by simply manipulating magnet positions (active mode) as well as size-based droplet separation with a fixed magnet position (passive mode). PMID:25332742

  13. Nucleoside-Based Ultrasensitive Fluorescent Probe for the Dual-Mode Imaging of Microviscosity in Living Cells.

    PubMed

    Li, Jianping; Zhang, Yanyan; Zhang, Hua; Xuan, Xiaopeng; Xie, Mingsheng; Xia, Shuang; Qu, Guirong; Guo, Haiming

    2016-05-17

    Microviscosity changes of living cells have a far-reaching influence on diffusion and movement capacity of RNA and, more seriously, could modify RNA functions in living cells. Fluorescent rotor, whose fluorescence responds to different environmental viscosities, holds great potential for the imaging of viscosity in biosystem. Although many fluorescent rotors have been reported for viscosity, the fluorogenic rotor with ultrasensitivity for the determination of microviscosity (<10 cP) was rarely reported. Herein, we report a nucleoside-based two-photon fluorescent rotor (dABp-3) that can selectively and ultrasensitively image microviscosity in RNA region of living cells for the first time. 2'-Deoxyadenosine is selected as an electron donor to permit energy transfer via the acetylenic bond to acceptor, a typical boron dipyrromethene moiety. Another highlight, dABp-3 is based on 2'-deoxyadenosine, which result in its recognition capacity for RNA. dABp-3 with ultrasensitivity provides a varied linear response to the microrange viscosity (1.8-6.0 cP) in RNA region of living cells on dual-mode-two-photon ratio mode and fluorescence lifetime mode. After screening and optimization, advantageously, dABp-3 can be used to screen reticulocytes from mature blood cells of thrombosis models in vitro and in vivo because of targeting RNA, while simultaneously image microviscosity changes in these cells. So, dABp-3 as an analytical tool holds considerable promise for bioimaging and monitoring of microviscosity changes in complex biological systems. PMID:27118477

  14. Dual-mode on-demand droplet routing in multiple microchannels using a magnetic fluid as carrier phase.

    PubMed

    Kim, Jitae; Won, June; Song, Simon

    2014-09-01

    We present dual-mode, on-demand droplet routing in a multiple-outlet microfluidic device using an oil-based magnetic fluid. Magnetite (Fe3O4) nanoparticle-contained oleic acid (MNOA) was used as a carrier phase for droplet generation and manipulation. The water-in-MNOA droplets were selectively distributed in a curved microchannel with three branches by utilizing both a hydrodynamic laminar flow pattern and an external magnetic field. Without the applied magnetic field, the droplets travelled along a hydrodynamic centerline that was displaced at each bifurcating junction. However, in the presence of a permanent magnet, they were repelled from the centerline and diverted into the desired channel when the repelled distance exceeded the minimum offset allocated to the channel. The repelled distance, which is proportional to the magnetic field gradient, was manipulated by controlling the magnet's distance from the device. To evaluate routing performance, three different sizes of droplets with diameters of 63, 88, and 102 μm were directed into designated outlets with the magnet positioned at varying distances. The result demonstrated that the 102-μm droplets were sorted with an accuracy of ∼93%. Our technique enables on-demand droplet routing in multiple outlet channels by simply manipulating magnet positions (active mode) as well as size-based droplet separation with a fixed magnet position (passive mode). PMID:25332742

  15. Redoxable heteronanocrystals functioning magnetic relaxation switch for activatable T1 and T2 dual-mode magnetic resonance imaging.

    PubMed

    Kim, Myeong-Hoon; Son, Hye-Young; Kim, Ga-Yun; Park, Kwangyeol; Huh, Yong-Min; Haam, Seungjoo

    2016-09-01

    T1/T2 dual-mode magnetic resonance (MR) contrast agents (DMCAs) have gained much attention because of their ability to improve accuracy by providing two pieces of complementary information with one instrument. However, most of these agents are "always ON" systems that emit MR contrast regardless of their interaction with target cells or biomarkers, which may result in poor target-to-background ratios. Herein, we introduce a rationally designed magnetic relaxation switch (MGRS) for an activatable T1/T2 dual MR imaging system. Redox-responsive heteronanocrystals, consisting of a superparamagnetic Fe3O4 core and a paramagnetic Mn3O4 shell, are synthesized through seed-mediated growth and subsequently surface-modified with polysorbate 80. The Mn3O4 shell acts as both a protector of Fe3O4 in aqueous environments to attenuate T2 relaxation and as a redoxable switch that can be activated in intracellular reducing environments by glutathione. This simultaneously generates large amounts of magnetically decoupled Mn(2+) ions and allows Fe3O4 to interact with the water protons. This smart nanoplatform shows an appropriate hydrodynamic size for the EPR effect (10-100 nm) and demonstrates biocompatibility. Efficient transitions of OFF/ON dual contrast effects are observed by in vitro imaging and MR relaxivity measurements. The ability to use these materials as DMCAs is demonstrated via effective passive tumor targeting for T1- and T2-weighted MR imaging in tumor-bearing mice. PMID:27281684

  16. Distinct modes of dopamine and GABA release in a dual transmitter neuron

    PubMed Central

    Borisovska, Maria; Bensen, AeSoon; Chong, Gene; Westbrook, Gary L.

    2013-01-01

    We now know of a surprising number of cases where single neurons contain multiple neurotransmitters. Neurons that contain a fast-acting neurotransmitter such as glutamate or GABA, and a modulatory transmitter such as dopamine are a particularly interesting case because they presumably serve dual signaling functions. The olfactory bulb contains a large population of GABA and dopamine-containing neurons, which have been implicated in normal olfaction as well as in Parkinson’s disease. Yet, they have been classified as non-exocytotic catecholamine neurons because of the apparent lack of vesicular monoamine transporters. Thus we examined how dopamine is stored and released from tyrosine-hydroxylase-positive-GFP (TH+-GFP) mouse periglomerular neurons in vitro. TH+ cells expressed both VMAT2 and VGAT, consistent with vesicular storage of both dopamine and GABA. Carbon fiber amperometry revealed that release of dopamine was quantal and calcium-dependent, but quantal size was much less than expected for large dense core vesicles, suggesting that release originated from EM-identified small clear vesicles. A single action potential in a TH+ neuron evoked a brief GABA synaptic current whereas evoked dopamine release was asynchronous, lasting for tens of seconds. Our data suggests that dopamine and GABA serve temporally distinct roles in these dual transmitter neurons. PMID:23365218

  17. Dual mode of degradation of Cdc25 A phosphatase

    PubMed Central

    Donzelli, Maddalena; Squatrito, Massimo; Ganoth, Dvora; Hershko, Avram; Pagano, Michele; Draetta, Giulio F.

    2002-01-01

    The Cdc25 dual-specificity phosphatases control progression through the eukaryotic cell division cycle by activating cyclin-dependent kinases. Cdc25 A regulates entry into S-phase by dephosphorylating Cdk2, it cooperates with activated oncogenes in inducing transformation and is overexpressed in several human tumors. DNA damage or DNA replication blocks induce phosphorylation of Cdc25 A and its subsequent degradation via the ubiquitin–proteasome pathway. Here we have investigated the regulation of Cdc25 A in the cell cycle. We found that Cdc25 A degradation during mitotic exit and in early G1 is mediated by the anaphase-promoting complex or cyclosome (APC/C)Cdh1 ligase, and that a KEN-box motif in the N-terminus of the protein is required for its targeted degradation. Interestingly, the KEN-box mutated protein remains unstable in interphase and upon ionizing radiation exposure. Moreover, SCF (Skp1/Cullin/F-box) inactivation using an interfering Cul1 mutant accumulates and stabilizes Cdc25 A. The presence of Cul1 and Skp1 in Cdc25 A immunocomplexes suggests a direct involvement of SCF in Cdc25 A degradation during interphase. We propose that a dual mechanism of regulated degradation allows for fine tuning of Cdc25 A abundance in response to cell environment. PMID:12234927

  18. Polysulfated Trehalose as a Novel Anticoagulant Agent with Dual Mode of Action

    PubMed Central

    Rashid, Qudsia; Abid, Mohammad; Gupta, Neha; Tyagi, Tarun; Ashraf, Mohammad Z.; Jairajpuri, Mohamad Aman

    2015-01-01

    Physiological hemostatic balance is a coordinated outcome of counteracting coagulation and fibrinolytic systems. An imbalance of procoagulant and anticoagulant factors may result in life threatening thromboembolism. Presently, anticoagulant administration is the first line of therapy for the treatment of these conditions and several anticoagulants have been approved, including various forms of heparin. However, the polyanionic nature and multispecificity of heparin pose several complications. Generally, the polysulfated compounds with antithrombotic potential are thought to have feasible synthetic procedures with much less bleeding, thus having favourable safety profiles. Here we report the synthesis of a novel compound, trehalose octasulfate and the assessment of its anticoagulation potential. Molecular docking of trehalose and trehalose octasulfate with antithrombin showed a specificity switch in binding affinity on sulfation, where trehalose octasulfate interacts with critical residues of AT that are either directly involved in heparin binding or in the conformational rearrangement of AT on heparin binding. An in vitro analysis of trehalose octasulfate demonstrated prolonged clotting time. Lead compound when intravenously injected in occlusion induced thrombotic rats showed remarkable reduction in the size and weight of the clot at a low dose. Delay in coagulation time was observed by analysing blood plasma isolated from rats preinjected with trehalose octasulfate. A decrease in Adenosine 5′-Diphosphate (ADP) induced platelet aggregation indicated a probable dual anticoagulant and antiplatelet mechanism of action. To summarize, this study presents trehalose octasulfate as a novel, effective, dual acting antithrombotic agent. PMID:25866798

  19. A wavelength-switchable single-longitudinal-mode dual-wavelength erbium-doped fiber laser for switchable microwave generation.

    PubMed

    Pan, Shilong; Yao, Jianping

    2009-03-30

    A novel wavelength-switchable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber laser (EDFL) implemented based on a sigma architecture that is composed of a ring loop and a linear standing wave arm is experimentally demonstrated. Gain competition that prevents stable dual-wavelength oscillation is effectively suppressed by placing the gain medium in the standing-wave arm and by introducing polarization hole burning (PHB) via polarization multiplexing of the two lasing wavelengths in the ring loop. The SLM operation is guaranteed by an ultranarrow Fabry- Perot filter (FPF) introduced by absorption saturation in an unpumped erbium-doped fiber (EDF) and the gain saturation in the gain medium. In addition, the ring cavity forms a Lyot filter for each wavelength. Thus, wavelength switching is achieved by simply adjusting the polarization state of either wavelength. By beating the two SLM wavelengths at a photodetector (PD), a microwave signal with a frequency tunable from approximately 10 to approximately 50 GHz is experimentally generated. PMID:19333306

  20. Development of Real-Time Dual-Display Handheld and Bench-Top Hybrid-Mode SD-OCTs

    PubMed Central

    Cho, Nam Hyun; Park, Kibeom; Wijesinghe, Ruchire Eranga; Shin, Yong Seung; Jung, Woonggyu; Kim, Jeehyun

    2014-01-01

    Development of a dual-display handheld optical coherence tomography (OCT) system for retina and optic-nerve-head diagnosis beyond the volunteer motion constraints is reported. The developed system is portable and easily movable, containing the compact portable OCT system that includes the handheld probe and computer. Eye posterior chambers were diagnosed using the handheld probe, and the probe could be fixed to the bench-top cradle depending on the volunteers' physical condition. The images obtained using this handheld probe were displayed in real time on the computer monitor and on a small secondary built-in monitor; the displayed images were saved using the handheld probe's built-in button. Large-scale signal-processing procedures such as k-domain linearization, fast Fourier transform (FFT), and log-scaling signal processing can be rapidly applied using graphics-processing-unit (GPU) accelerated processing rather than central-processing-unit (CPU) processing. The Labview-based system resolution is 1,024 × 512 pixels, and the frame rate is 56 frames/s, useful for real-time display. The 3D images of the posterior chambers including the retina, optic-nerve head, blood vessels, and optic nerve were composed using real-time displayed images with 500 × 500 × 500 pixel resolution. A handheld and bench-top hybrid mode with a dual-display handheld OCT was developed to overcome the drawbacks of the conventional method. PMID:24473286

  1. Development of real-time dual-display handheld and bench-top hybrid-mode SD-OCTs.

    PubMed

    Cho, Nam Hyun; Park, Kibeom; Wijesinghe, Ruchire Eranga; Shin, Yong Seung; Jung, Woonggyu; Kim, Jeehyun

    2014-01-01

    Development of a dual-display handheld optical coherence tomography (OCT) system for retina and optic-nerve-head diagnosis beyond the volunteer motion constraints is reported. The developed system is portable and easily movable, containing the compact portable OCT system that includes the handheld probe and computer. Eye posterior chambers were diagnosed using the handheld probe, and the probe could be fixed to the bench-top cradle depending on the volunteers' physical condition. The images obtained using this handheld probe were displayed in real time on the computer monitor and on a small secondary built-in monitor; the displayed images were saved using the handheld probe's built-in button. Large-scale signal-processing procedures such as k-domain linearization, fast Fourier transform (FFT), and log-scaling signal processing can be rapidly applied using graphics-processing-unit (GPU) accelerated processing rather than central-processing-unit (CPU) processing. The Labview-based system resolution is 1,024 × 512 pixels, and the frame rate is 56 frames/s, useful for real-time display. The 3D images of the posterior chambers including the retina, optic-nerve head, blood vessels, and optic nerve were composed using real-time displayed images with 500 × 500 × 500 pixel resolution. A handheld and bench-top hybrid mode with a dual-display handheld OCT was developed to overcome the drawbacks of the conventional method. PMID:24473286

  2. Development and Operation of Dual-Mode Analyzers for Wireless Power Consortium/Power Matters Alliance Wireless Power Systems.

    PubMed

    Um, Keehong

    2016-05-01

    We have designed a protocol analyzer to be used in wireless power systems and analyzed the operation of wireless chargers defined by standards of Qi of Wireless Power Consortium (WPC) and Power Matters Alliance (PMA) protocols. The integrated circuit (IC, or microchip) developed so far for wireless power transmission is not easily adopted by chargers for specific purposes. A device for measuring the performance of test equipment currently available is required to transform and expand the types of protocol. Since a protocol analyzer with these functions is required, we have developed a device that can analyze the two protocols of WPC and PMA at the same time. As a result of our research, we present a dual-mode system that can analyze the protocols of both WPC and PMA. PMID:27483911

  3. Design of a search and rescue terminal based on the dual-mode satellite and CDMA network

    NASA Astrophysics Data System (ADS)

    Zhao, Junping; Zhang, Xuan; Zheng, Bing; Zhou, Yubin; Song, Hao; Song, Wei; Zhang, Meikui; Liu, Tongze; Zhou, Li

    2010-12-01

    The current goal is to create a set of portable terminals with GPS/BD2 dual-mode satellite positioning, vital signs monitoring and wireless transmission functions. The terminal depends on an ARM processor to collect and combine data related to vital signs and GPS/BD2 location information, and sends the message to headquarters through the military CDMA network. It integrates multiple functions as a whole. The satellite positioning and wireless transmission capabilities are integrated into the motherboard, and the vital signs sensors used in the form of belts communicate with the board through Bluetooth. It can be adjusted according to the headquarters' instructions. This kind of device is of great practical significance for operations during disaster relief, search and rescue of the wounded in wartime, non-war military operations and other special circumstances.

  4. Dual-Mode Luminescence Modulation upon Visible-Light-Driven Photochromism with High Contrast for Inorganic Luminescence Ferroelectrics.

    PubMed

    Zhang, Qiwei; Zheng, Xuewen; Sun, Haiqin; Li, Wenqing; Wang, Xusheng; Hao, Xihong; An, Shengli

    2016-02-01

    A luminescence ferroelectric oxide, Na(0.5)Bi(2.5)Nb2O9 (NBN), system with bismuth layer structure introduced by lanthanide ion (Er(3+)) has been demonstrated to exhibit reversible, high-contrast luminescence modulation (95%) and excellent fatigue resistance based on visible-light-driven photochromism (407 nm or sunlight). The coloration and decoloration process can be effectively read out by dual modes, upconversion and downshifting, and reversibly converted between green and dark gray by alternating visible light or sunlight irradiation and thermal stimulus. The luminescence modulation degree upon photochromic reactions is strongly dependent upon irradiation light wavelength and irradiation time. After undergoing several cycles, there are no significant degradations, showing high reversibility. Considering its high-contrast photoswitchable luminescence feature and intrinsic ferroelectricity of NBN host, NBN-based multifunctional materials can be suggested as a promising candidate for new potentials in photonic storage and optoelectronic multifunctional devices. PMID:26820999

  5. Design of single-polarization single-mode coupler based on dual-core photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Wang, Guochen; Wang, Zhenpeng; Yu, Fei

    2016-02-01

    A single-polarization single-mode (SPSM) photonic crystal fiber (PCF) coupler is designed and investigated by using full-vector finite-element method with the anisotropic perfectly matched layer. We numerically analyze the SPSM coupling properties with respect to the structure parameters and confinement loss characteristics. The results reveal that the coupling length between dual cores is as small as millimeter order of magnitude due to the wide silica bridge of energy transfer, and the SPSM coupling region can be tailored to cover the communication windows of 1.3 or 1.55 μm with optimized design parameters. Moreover, the confinement loss of x polarization is 3 orders of magnitude larger than that of y polarization in single polarization range. The proposed SPSM PCF coupler may find application in polarization-sensitive systems.

  6. TDMA-Based Dual-Mode Communication for Mobile Wireless Sensor Networks

    PubMed Central

    Mehta, Ankur; Kerkez, Branko; Glaser, Steven D.; Pister, Kristofer S. J.

    2012-01-01

    Small highly mobile robots, and in particular micro air vehicles (MAVs), are well suited to the task of exploring unknown indoor environments such as buildings and caves. Such a task imposes a number of requirements on the underlying communication infrastructure, with differing goals during various stages of the mission. This work addresses those requirements with a hybrid communications infrastructure consisting of a stationary mesh network along with the mobile nodes. The combined network operates in two independent modes, coupling a highly efficient, low duty cycle, low throughput mode for routing and persistent sensing with a burst mode for high data rate communication. By strategically distributing available frequency channels between the mobile agents and the stationary nodes, the overall network provides reliable long-term communication paths while maximizing data throughput when needed. PMID:23443374

  7. TDMA-based dual-mode communication for mobile wireless sensor networks.

    PubMed

    Mehta, Ankur; Kerkez, Branko; Glaser, Steven D; Pister, Kristofer S J

    2012-01-01

    Small highly mobile robots, and in particular micro air vehicles (MAVs), are well suited to the task of exploring unknown indoor environments such as buildings and caves. Such a task imposes a number of requirements on the underlying communication infrastructure, with differing goals during various stages of the mission. This work addresses those requirements with a hybrid communications infrastructure consisting of a stationary mesh network along with the mobile nodes. The combined network operates in two independent modes, coupling a highly efficient, low duty cycle, low throughput mode for routing and persistent sensing with a burst mode for high data rate communication. By strategically distributing available frequency channels between the mobile agents and the stationary nodes, the overall network provides reliable long-term communication paths while maximizing data throughput when needed. PMID:23443374

  8. Polarization-insensitive liquid crystal microlens array with dual focal modes.

    PubMed

    Hsu, Che-Ju; Liao, Chen-Hau; Chen, Bao-Long; Chih, Shang-Yi; Huang, Chi-Yen

    2014-10-20

    We demonstrate a liquid crystal (LC) microlens array (MLA) fabricated by LCs possessing negative dielectric anisotropy, in conjunction with a cell with a three-electrode structure. The presented LC MLA is polarization-insensitive and can be operated in both concave and convex modes. The shortest focal length of the LC MLA is -2.54 and 2.22 mm in concave and convex mode, respectively. Disclination lines that are usually observed in conventional hole-patterned LC lens can also be avoided because of the vertical alignment treatment of LCs. PMID:25401625

  9. Direct observation of the core/double-shell architecture of intense dual-mode luminescent tetragonal bipyramidal nanophosphors.

    PubMed

    Kim, Su Yeon; Jeong, Jong Seok; Mkhoyan, K Andre; Jang, Ho Seong

    2016-05-21

    Highly efficient downconversion (DC) green-emitting LiYF4:Ce,Tb nanophosphors have been synthesized for bright dual-mode upconversion (UC) and DC green-emitting core/double-shell (C/D-S) nanophosphors-Li(Gd,Y)F4:Yb(18%),Er(2%)/LiYF4:Ce(15%),Tb(15%)/LiYF4-and the C/D-S structure has been proved by extensive scanning transmission electron microscopy (STEM) analysis. Colloidal LiYF4:Ce,Tb nanophosphors with a tetragonal bipyramidal shape are synthesized for the first time and they show intense DC green light via energy transfer from Ce(3+) to Tb(3+) under illumination with ultraviolet (UV) light. The LiYF4:Ce,Tb nanophosphors show 65 times higher photoluminescence intensity than LiYF4:Tb nanophosphors under illumination with UV light and the LiYF4:Ce,Tb is adapted into a luminescent shell of the tetragonal bipyramidal C/D-S nanophosphors. The formation of the DC shell on the core significantly enhances UC luminescence from the UC core under irradiation of near infrared light and concurrently generates DC luminescence from the core/shell nanophosphors under UV light. Coating with an inert inorganic shell further enhances the UC-DC dual-mode luminescence by suppressing the surface quenching effect. The C/D-S nanophosphors show 3.8% UC quantum efficiency (QE) at 239 W cm(-2) and 73.0 ± 0.1% DC QE. The designed C/D-S architecture in tetragonal bipyramidal nanophosphors is rigorously verified by an energy dispersive X-ray spectroscopy (EDX) analysis, with the assistance of line profile simulation, using an aberration-corrected scanning transmission electron microscope equipped with a high-efficiency EDX. The feasibility of these C/D-S nanophosphors for transparent display devices is also considered. PMID:26729043

  10. Fabrication of a novel dual mode cholesterol biosensor using titanium dioxide nanowire bridged 3D graphene nanostacks.

    PubMed

    Komathi, S; Muthuchamy, N; Lee, K-P; Gopalan, A-I

    2016-10-15

    Herein, we fabricated a novel electrochemical-photoelectrochemical (PEC) dual-mode cholesterol biosensor based on graphene (G) sheets interconnected-graphene embedded titanium nanowires (TiO2(G)-NWs) 3D nanostacks (designated as G/Ti(G) 3DNS) by exploiting the beneficial characteristics of G and TiO2-NWs to achieve good selectivity and high sensitivity for cholesterol detection. The G/Ti(G) 3DNS was fabricated by the reaction between functionalized G and TiO2(G)-NWs. Cholesterol oxidase (ChOx) was subsequently immobilized in to G/Ti(G) 3DNS using chitosan (CS) as the binder and the dual mode G/Ti(G) 3DNS/CS/ChOx biosensor was fabricated. The electro-optical properties of the G/Ti(G) 3DNS/CS/ChOx bioelectrode were characterized by cyclic voltammetry and UV-vis diffuse reflection spectroscopy. The cyclic voltammetry of immobilized ChOx showed a pair of well-defined redox peaks indicating direct electron transfer (DET) of ChOx. The amperometric reduction peak current (at -0.05V) linearly increased with increase in cholesterol concentration. The G/Ti(G) 3DNS/CS/ChOx bioelectrode was selective to cholesterol with a remarkable sensitivity (3.82μA/cm(2)mM) and a lower detection limit (6μM). Also, G/Ti(G) 3DNS/CS/ChOx functioned as photoelectrode and exhibited selective detection of cholesterol under a low bias voltage and light irradiation. Kinetic parameters, reproducibility, repeatability, storage stability and effect of temperature and pH were evaluated. We envisage that G/Ti(G) 3DNS with its prospective characteristics, would be a promising material for wide range of biosensing applications. PMID:26611566