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Abstract Two three-dimensional metal-organic frameworks {CdNa 2 (H 2 O) 2 (DMF)[(ML) 2 Na(H 2 O) 2 ]}·6H 2 O (L = C 22 H 18 N 2 O 6 ; M = Ni 1 , Cu 2) based on carboxylate-functionalized salen ligands were successfully synthesized by one-step synthesis of reacting 1,2-cyclohexanediamine- N , N ′-bis-(3-carboxylsalicylide) (H 4 L) with metal acetate. Both of them were characterized by single-crystal X-ray diffraction, powder X-ray diffraction (XPRD), elemental analysis, TG analysis, IR and UV–visible spectroscopy. X-ray Single-crystal structural analysis reveals that compounds 1 and 2 are isostructural, which display a 3D porous framework constructed by infinite [CdNa 2 (H 2 O) 2 (DMF)(COO) 4 ] n chains as nodes and [(ML) 2 Na(H 2 O) 2 ] (M = Ni 1 , Cu 2) units as linkers. They present the first examples of metal-salen-based MOFs constructed by heterometallic inorganic node. In addition, magnetic studies indicate that ferromagnetic interactions exist in compound 1. Graphical abstract Two metal-organic frameworks 1 and 2 based on carboxylate-functionalized salen ligands were successfully obtained by one-step synthesis. 1 and 2 are isostructural, which display a porous framework constructed by infinite [CdNa 2 (H 2 O) 2 (DMF)(COO) 4 ] n chains as nodes and [(ML) 2 Na(H 2 O) 2 ] (M = Ni 1 , Cu 2) units as linkers. Unlabelled Image Highlights • Compounds 1 and 2 present the first examples of metal-salen-based MOFs constructed by heterometallic inorganic node. • Compounds 1 and 2 were obtained by one-step synthesis without the preparation of “metalloligand” in advance. • Magnetic studies indicate that ferromagnetic interactions exist in compound 1. [ABSTRACT FROM AUTHOR]

A wireless deep-subwavelength metamaterial architecture is proposed, modeled and demonstrated for a high-resolution magnetic resonance imaging (HR-MRI) application that is miniaturized to be resonant at approximately λ 0 /1500 dimensions. The proposed structure has the adjustable resonance frequency from 65 MHz to 5.5 GHz for the sub-cm footprint area (8 mm × 8 mm for this study) and provides a quality factor (Q-factor) of approximately 80 in free space for 123 MHz of operation. This structure consists of a cross-via metallized partial-double-layer metamaterial, sandwiching a dielectric thin film; this structure strongly localizes the electric field in this film and has a highly capacitive metal overlay that allows for a wide range of frequency adjustment. Although the achieved resonance frequencies enable a large number of applications, as a proof-of-concept demonstration, we experimentally showed the operation of this wireless metastructure in HR-MRI to highlight its precise frequency adjustment and signal-to-noise-ratio (SNR) improvement capabilities. The proposed metamaterial was found to maintains high Q-factors despite loading with a body-mimicking lossy phantom. The experimental results indicated that the proposed metastructure can be used as an SNR-enhancing device offering 15-fold SNR enhancements that allows for imaging of objects as small as 200 μm in diameter in its vicinity, at an unprecedented level of resolution at the given DC field using standard head coils. As a result of its deep-subwavelength miniaturization accompanied by reasonable Q-factor with outstanding resonance frequency adjustment capability, this class of metastructure is proved to be an excellent candidate for in vivo medical applications. [ABSTRACT FROM AUTHOR]

Capacitive input couplers based on a 50 Ω coaxial transmission line are frequently used to transmit RF power to superconducting (SC) resonators operating in CW mode. It is well known that coaxial transmission lines are prone to multipacting phenomenon in a wide range of RF power level and operating frequency. The Facility for Rare Isotope Beams (FRIB) being constructed at Michigan State University includes two types of quarter wave SC resonators (QWR) operating at 80.5 MHz and two types of half wave SC resonators (HWR) operating at 322 MHz. As was reported in ref. [1] a capacitive input coupler used with HWRs was experiencing strong multipacting that resulted in a long conditioning time prior the cavity testing at design levels of accelerating fields. We have developed an insert into 50 Ω coaxial transmission line that provides opportunity to bias the RF coupler antenna and protect the amplifier from the bias potential in the case of breakdown in DC isolation. Two of such devices have been built and are currently used for the off-line testing of 8 HWRs installed in the cryomodule. [ABSTRACT FROM AUTHOR]

A Digital Loudspeaker Array (DLA) is an electro-mechanical transductor which receives a numerical signal as input data and allows the analogical conversion directly in the air. We designed PZT actuated membranes in order to obtain the highest acoustic pressure as possible. We built 256-MEMS-membranes DLAs using a generic PZT technology and digital acoustic reconstructions of the sound have been already demonstrated using our MEMS-DLA. In this paper, using FEM simulations, we evidence that residual stresses are responsible of the high distortion level measured on our demonstrators. A stress compensated technology was established using FEM approach. Acoustic characterization of stress compensated demonstrators proves distortion decreased and validates our hypothesis. [ABSTRACT FROM AUTHOR]

To increase the effective actuation stroke of piezoelectric stack actuators and giant magnetostrictive actuators, displacement amplifiers are usually employed to provide mechanical amplification. In this work, a novel symmetric two-stage lever-type amplifier called tensural displacement amplifier is proposed, in which all the flexural hinges are loaded in tension and bending rather than compression and bending when deflected. The tensural displacement amplifier does not have the potential problems buckling may cause because all the compliant members are loaded in tension. In addition, the proposed amplifier exhibits higher lateral frequency when deflected due to the stress stiffening effects of the tensural hinges. The kinetostatic model for the tensural displacement amplifier was established, based on which an amplifier whose amplification ratio exceeds 40 was designed. The amplification ratio of the design was further verified by the finite element model and prototype test. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Scalp-derived human somatosensory evoked potentials (SEPs) contain high-frequency oscillations (600Hz; ‘sigma-burst’) reflecting concomitant bursts of spike responses in primary somatosensory cortex that repeat regularly at 600Hz. Notably, recent human intracranial SEP have revealed also 1kHz responses (‘kappa-burst’), possibly reflecting non-rhythmic spiking summed over multiple cells (MUA: multi-unit activity). However, the non-invasive detection of EEG signals at 1kHz typical for spikes has always been limited by noise contributions from both, amplifier and body/electrode interface. Accordingly, we developed a low-noise recording set-up optimised to map non-invasively 1kHz SEP components. Methods: SEP were recorded upon 4Hz left median nerve stimulation in 6 healthy human subjects. Scalp potentials were acquired inside an electrically and magnetically shielded room using low-noise custom-made amplifiers. Furthermore, in order to reduce thermal Johnson noise contributions from the sensor/skin interface, electrode impedances were adjusted to ⩽1kΩ. Responses averaged after repeated presentation of the stimulus (n =4000 trials) were evaluated by spatio-temporal pattern analyses in complementary spectral bands. Results: Three distinct spectral components were identified: N20 (<100Hz), sigma-burst (450–750Hz), and kappa-burst (850–1200Hz). The two high-frequency bursts (sigma, kappa) exhibited distinct and partially independent spatiotemporal evolutions, indicating subcortical as well as several cortical generators. Conclusions: Using a dedicated low-noise set-up, human SEP ‘kappa-bursts’ at 1kHz can be non-invasively detected and their scalp distribution be mapped. Their topographies indicate a set of subcortical/cortical generators, at least partially distinct from the topography of the 600Hz sigma-bursts described previously. Significance: The non-invasive detection and surface mapping of 1kHz EEG signals presented here provides an essential step towards non-invasive monitoring of multi-unit spike activity. [Copyright &y& Elsevier]

Abstract: An immunoassay based on the enrichment of antibodies by magnetic beads (MB) and their subsequent detection of antigens in a microfluidic chip (MFC)–quartz crystal microbalance (QCM) was developed and investigated. The MB conjugated to goat anti-human-immunoglobulin G (MB-anti-h-IgG) were concentrated within microchannels by the application of a magnetic field, which also functioned as a separation switch outside the MFC. The conjugation of the MB and the anti-h-IgG antibody in the MFC was completed in 1min. Removal of the magnetic field allowed the resulting tributary buffer solution to flush the MB-anti-h-IgG out of the MFC and onto a QCM chip. The combination of the MB-anti-h-IgG and the QCM chip amplified the detection sensitivity of antigen(s) to 10−1 ng/ml. By controlling the enrichment velocity and sample injection mode in the MFC, a linear response ranging from 10−1 to 103 ng/ml was obtained. This technique establishes a simple, rapid MFC method for the amplification of a QCM-based immunoassay. [Copyright &y& Elsevier]

Abstract: Saturable reactor or transductor used as a magnetic modulator or amplifier for the measurement of the small value DC output signal of a transducer may suffer from error due to the fact that a part of the current drawn from the transducer by the transductor unit is utilized to magnetize the core material. In this paper a modified two core saturable reactor circuit has been proposed to eliminate this error. This unit also minimizes some other errors like common mode error, material error, etc. Theory of operation and design of the circuit has been explained in this paper. The circuit has been tested by using a millivolt input signal as well as a thermocouple to measure temperature. The experimental results are presented in this paper. Linear static characteristic graphs have been observed. [Copyright &y& Elsevier]

Abstract: Magnetic properties of the planar structure consisting of a ferromagnetic metal and the diluted magnetic semiconductor are considered (by the example of the structure Fe/Ga(Mn)As, experimentally studied in [F. Maccherozzi, M. Sperl, G. Panaccione, J. Mina''r, S. Polesya, H. Ebert, U. Wurstbauer, M. Hochstrasser, G. Rossi, G. Woltersdorf, W. Wegscheider, C.H. Back, Phys. Rev. Lett. 101 (2008) 267201]). In the framework of the mean field theory, we demonstrate the presence of the significant amplification of the ferromagnetism, induced by the ferromagnetic metal in the near-interface semiconductor area, due to the indirect interaction of magnetic impurities. This results in the substantial expansion of the temperature range where the magnetization in the boundary semiconductor region exists, that might be important for possible practical applications. [Copyright &y& Elsevier]

Abstract: The JET plasma requires a radial magnetic field to control its vertical position and the bulk field is produced using relatively slow (line commutated) amplifiers. Should fast (possibly of order 100μs) disturbances arise, the plasma can move from its reference position and this must be controlled using a high-speed amplifier. As part of a wider project to upgrade the plasma control system, a new, more powerful, enhanced radial field amplifier (ERFA) will be installed to replace the existing fast radial field amplifier (FRFA). The company JEMA designed the ERFA to meet the technical requirements specified in the Call-for-tender document and it comprises four series-connected Units with a total rated output voltage of ±12kV, in 3kV steps, and a maximum output current of ±5kA. The ERFA is being manufactured at JEMA''s works during 2008 so that it can be installed, tested and then commissioned on the JET radial field load coils in spring 2009. [Copyright &y& Elsevier]

Abstract: When driving an inductive link with a class E inverter, only little variation can be tolerated on the inductance value of the transmitting coil. Flexible or deformable coils are hence not compatible with a classic open-loop class E design. To tackle this limitation, a transductor—having an electrically controllable inductance value—is placed in series with the deformable coil. A control loop steers the transductor to the appropriate inductance value while the transmitting coil is being deformed. Based on this principle, a class E driver for deformable coils was realised that works at a frequency of 132 kHz and has an output magnetomotive force of 125ampere-turns. Class E regime and a fixed output current are maintained for inductance variations up to 27%. The principal advantage of transductor compensation compared to earlier reported techniques, is that the operation frequency remains untouched. [Copyright &y& Elsevier]

Abstract: In the development of biosensors, organic phase enzyme electrodes (OPEEs) have received considerable attention for the detection of substrates in organic media. This article reviews different enzymes, transductors and immobilization methods used for the preparation of OPEEs in the last decade. [Copyright &y& Elsevier]

This paper describes a new approach for realizing digitally programmable VHF/UHF transconductors compatible with pure digital CMOS technologies. A programmable/tunable transconductor, based on a parallel connection of unit cascode cells, is used to implement a fully balanced current-mode Gm–C integrator to operate over the 30–200 MHz range with more than 70 dB of dynamic range for 1% of THD. [Copyright &y& Elsevier]

The conventional single core or two core saturable reactor or transductor used for dc busbar current measurement may suffer from errors due to the magnetisation component of the dc flux and the asymmetry of the core materials. In the present paper a feedback technique of this type of dc current measurement has been developed. In this technique, the output signal has been used to send a feedback current through a feedback winding in order to nullify the magnetisation component of the dc flux and thus the measurement may be assumed to be more accurate with respect to other similar instruments. The developed network has been studied up to a dc busbar current of 50 A and the output characteristic has been found to be quite linear. The design of the network, its principle of operation and experimental data are reported in the present paper. [Copyright &y& Elsevier]

This paper suggests a parallel resistor to reduce DC time constant and DC response time of the transient response, induced immediately after an AC voltage connected to a bolt-clamped Langevin transducer (BLT) is switched off. An equivalent circuit is first expressed. Then, an open-circuit transient response at the terminals induced by initial states is derived and measured, and thus parameters for losses of the BLT device are estimated by DC and AC time constants of the transient response. Moreover, a driving and measuring system is designed to determine transient response and steady-state responses of the BLT device, and a parallel resistor is connected to the BLT device to reduce the DC time constant. Experimental results indicate that the DC time constant greatly exceeds the AC time constant without the parallel resistor, and greatly decreases from 42 to 1 ms by a 100-kΩ parallel resistor. [Copyright &y& Elsevier]

We theoretically and experimentally investigate the static and dynamic properties of two-stage L-band erbium-doped fiber amplifiers (EDFAs) that are partially gain-clamped. Partial (all-optical) gain-clamping is obtained by forming a fiber grating laser in either the first or the second stage of the two-stage EDFA. Although the amplifiers are only partially gain-clamped, results show that they exhibit good gain-clamped characteristics. Furthermore, the amplifier configuration in which the second stage is gain-clamped can have a very low noise figure and a small transient gain (power) excursion. [Copyright &y& Elsevier]

While there is increasing evidence that chondrocytes are affected by mechanically induced stimuli, endogenous force-related electrical potentials within articular cartilage have been so far observed only in-vitro. Using a porkine ex-vivo model (German Land Race), 8 knee joints were explanted and exposed to mechanical force (up to 800 N) using a special device. Electrodes were inserted into the cartilage matrix. With an amplifier and an A/D transducer the changes of electrical voltage between the electrodes as well as those of the force were recorded online and simultaneously on a computer. Additionally, we located one pair of electrodes on the surface of the cartilage tissue to detect electrical fields outside the cartilage tissue. In relation to the applied force we observed that electrical potentials derived from inside and outside the articular cartilage showed a correspondence. When an alternating force with an amplitude of 360 N and a frequency of about 0.2 Hz was periodically applied, we measured peak amplitudes ranging from 2.1 to 5.5 mV within the cartilage tissue with electrical negativity within the weight bearing area of the cartilage tissue. The measured voltages depended on the applied force, the location of the electrodes, and on anatomical variations. We found an almost linear relation between the magnitude of the applied force and the recorded voltage. With the help of the electrodes located outside and within the cartilage tissue, we were able to show that force dependent fields are generated inside the cartilage. There are several theories explaining the origin of these electrical phenomena, many of them focusing on the negative charges of the proteoglycans in relation to the flow of interstital fluid and ions under compression. However, the consequences of these phenomena are yet not clear. [Copyright &y& Elsevier]

Abstract: We present preparation and spectroscopic characterization of thulium-doped fibers with enhanced 3H4 fluorescence lifetime obtained by codoping with alumina. With an alumina content of 10mol%, a fluorescence lifetime of 58μs is achieved. For the first time we study and optimize the thulium-doped fiber amplifier (TDFA) with a dual-wavelength (800+1400nm) pumping scheme, where the pump at 800nm propagates in the cladding and the pump at 1400nm propagates in the core. In the study we use numerical simulations and experimentally obtained fiber characteristics. The results are compared with those obtained for numerical simulation of a TDFA pumped at a single wavelength in the 1050nm band. [Copyright &y& Elsevier]