Development of 2-2 piezoelectric ceramic/polymer composites by direct-write technique

The Micropen™ direct-write technique was used to fabricate ceramic skeletal structures to develop piezoelectric ceramic/polymer composites with 2–2 connectivity for medical imaging applications. A lead zirconate titanate PZT paste with ∼35 vol.% solids loading was prepared as a writing material and the paste’s rheological properties were characterized to evaluate its feasibly for Micropen deposition. A serpentine pattern was designed and deposited in AutoCAD and with a 100 μm pen tip, respectively. After debinding and sintering, the microstructural analysis showed that the ceramic structures were fully densified, with good bonding among layers. Typical single-layer thickness was ∼50 μm, and sintered line width was ∼120 μm. The composites containing 30–45 vol.% PZT were fabricated within 1 cm² area, with thicknesses ranging from 350 to 380 μm. Their electromechanical and dielectric properties were measured and found similar to that of composites fabricated by other techniques. The k _t was ∼0.61, d ₃₃ was 210–320, with Q _m of ∼6 and dielectric constant of 650–940.     

Thermoelectric properties of p-type Bi0.5Sb1.5Te3 compounds fabricated by spark plasma sintering

P-type thermoelectric Bi_0.5Sb_1.5Te₃ compounds were prepared by the spark plasma sintering method with temperature ranges of 300–420^∘C and powder sizes of ∼75 μm, 76–150 μm, 151–250 μm. As the sintering temperature increased, the electrical resistivity and thermal conductivity of the compound were greatly changed due to an increase in the relative density. The Seebeck coefficient and electrical resistivity were varied largely with decreasing the powder size. Subsequently, the compound sintered at 380^∘C with the powders of ∼75 μm showed the maximum figure-of-merit of 2.65 × 10⁻³K⁻¹ and the bending strength of 73 MPa.     

Changes in proton transverse relaxation times of rat myocardium that has suffered a previous oxidative insult

An oxidative insult can induce severe damage, as in the phenomenon of myocardial ischemia and reperfusion. However, there are situations in which the damage is not so obvious (e.g., silent ischemia or aging), and the negative effects will be seen only in time. Our aim was to reveal these small changes in the myofilaments by using the nuclear magnetic resonance (NMR) technique. We used Wistar rat hearts in a constant-pressure Langendorff system, perfused with oxygenated Krebs-Henseleit buffer at 37°C. After 15 minutes of stabilization, the hearts were perfused with buffer supplemented with H₂O₂ at 50, 75, or 100 μmol/L for 15 or 30 minutes. Fifteen-minute and 45-minute perfusion controls and unperfused hearts were also collected. Heart rate (HR) and left ventricular developed pressure (LVDP) were determined with the help of a latex balloon, inserted in the left ventricle and connected with a pressure transducer. Proton transverse relaxation times (T ₂) were determined at the end of the experiment.T ₂ values were measured again in the same tissue fragments after they had been glycerinated and incubated in relaxation and rigor media. The functional parameters (HR, LVDP, coronary flow) were not significantly changed in control and 50 μmol/L H₂O₂ groups but were increased in the 75 μmol/L H₂O₂ group and significantly decreased in the 100 μmol/L H₂O₂ group.T ₂ is significantly decreased in rigor media starting with 50 μmol/L H₂O₂ administrated for 30 minutes and does not correlate with dose and duration of the oxidative insult.T ₂ in rigor is shorter than in relaxation media within the groups, and this difference is increased in the treated hearts.     

Liver and spleen enhancement after intravenous injection of carboxydextran magnetite: effect of dose,delay of imaging,and field strength in anex vivo model

It has been predicted that liver and spleen enhancement after administration of superparamagnetic contrast agents may be different, depending on the strength of the main magnetic field. With the use of anex vivo model, we investigated at 0.3, 0.5, and 1.5 T the effects on liver and spleen signal intensity of 5, 15, and 45 µmol/kg body weight of dextran magnetite (SHU 555A) in 54 rats. Nine rats served as controls. At different time delays since injection, the animals were killed, and after perfusion with saline, the liver, brain, and spleen were fixed in formalin. The specimens were embedded in an agar gel matrix and imaged with inversion recovery T1-weighted, proton density spin echo, and T2*-weighted gradient recalled echo (GRE) sequences. At each magnetic field strength, peak liver and spleen signal loss increased with increasing dose of the contrast medium. Signal loss was significantly more conspicuous after a dose of 15 than 5 µmol/kg body weight, but not after a dose of 45 compared with 15 µmol/kg. No signal change was observed in the brain. GRE images showed higher enhancement than proton density-weighted spin echo and inversion recovery images but were noisier. The enhancement showed a plateau between 30 min and 24 hours. Only the signal decrease of the liver after a low dose of contrast medium on GRE images was significantly higher (p<0.01) at 1.5 than at 0.5 and 0.3 T. Other differences in respect to the field strength were less significant (p<0.05) or nonsignificant. Differences in the spleen enhancement were nonsignificant. SHU 555A at a dose of 15 µmol/kg is an efficient intracellular contrast agent for liver and spleen at low, mid, and high field strength. Proton density spin echo images are probably the sequence of choice to exploit SHU 555A contrast effects and a wide time window for imaging after its intravenous injection does exist.     

Complex permittivity and permeability of Co-substituted NiCuZn ferrite at rf and microwave frequencies

NiCuZn ferrite has recently attracted a lot of attention for its application in high frequency (up to a few GHz) multilayer chip inductors (MLCIs) and for other microwave devices owing to their favorable electromagnetic properties and low densification temperature. In order to study the effect of substitution of cations by cobalt in small concentration on the dielectric and magnetic properties at low and high frequencies, bulk polycrystalline ferrite samples of starting composition (Ni_0.2Cu_0.2Zn_0.6)_{1 − x} Co _x Fe₂O₄, having x = 0, 0.01, 0.03 and 0.05, were prepared by citrate precursor method. Pure spinel (cubic) ferrite formation was confirmed by powder X-ray diffraction technique. Complex permittivity and permeability were measured at microwave frequencies (X-band) using the cavity perturbation method, which is a non-contact method. The values of real part of permittivity (ε ′) vary in the range 7–9.6 and of the imaginary part (ε ″) vary from 0.020–0.120, whereas real part of the permeability (μ′) lies in the range 2.6–14.0 and the imaginary part of permeability (μ″) varies from 0.5–6.0. It is observed that there is an increase in μ′ and decrease in the magnetic loss (tan δ _μ) on increasing the cobalt concentration from x = 0 to x = 0.05. The variation of these parameters, both with frequency in X-band and with the cobalt concentration, is discussed in this paper.     

Droplets actuating chip based on electrowetting-on-dielectric

A droplet-based actuating chip by using the method of electrowetting-on-dielectric (EWOD) was developed to manipulate the microfluidics. Here, the actuation mechanism of the sandwiched-configuration EWOD chips was carefully studied, and the movement of droplets was numerically analyzed by using the computational fluidic software, CFD-ACE+. The fabrication of the chip, including a heavily phosphorus-doped poly-silicon micro-electrode array and a thermally grown SiO₂ dielectric layer, was exploited to improve the chip stability and decrease the actuation voltage. In experiments, the transportation of a deionized droplet of about 0.5 μL is successfully achieved in air by applying the low voltage of 45 V. Translated from Journal of Tsinghua University (Science and Technology), 2006, 46(7): 1 341–1 344 [译自: 清华大学学报 (自然科学版)]     

Magnetic resonance evaluation of autonomous thyroid nodules treated by percutaneous ethanol injection

Magnetic resonance (MR) imaging was used to evaluate the effect of ultrasound-guided percutaneous ethanol injection (PEI) of autonomous thyroid nodules (ATNs). Nine patients affected with ATN (3.7–32.2 mL volume) underwent PEI (4–19 mL ethanol, subdivided in 3–6 weekly procedures). MR imaging (1.5 T) was performed before each alcoholization and 1 month after the last PEI procedure with the following parameters:T ₁-(550/12) andT ₂-weighted (2200/160) spin-echo images; 4-mm slices, 10% gap; coronal planes. A further seven patients with normal thyroid function, who had undergone PEI 6–18 months before, underwent an MR examination with the same parameters. The signal-to-noise ratio (S/N) of ATN and extranodular gland, as well as ATN volume, were evaluated on theT ₂-weighted images. OnT ₁-weighted images, ATNs appeared mostly hypointense before treatment, with hyperintense areas during treatment, and were lightly hyperintense 6–18 months after treatment. S/N onT ₂-weighted images: extranodular gland 3.5–9.2; ATNs, before treatment 13.2–19.7, before the last procedure 7.7–11.6, 1 month after the last procedure 5.6–10.9; previously treated ATNs, 4.3–8.2. No significant volume reduction was observed with MR 1 month after the last procedure. The MR examination time was about 15 minutes. In conclusion, the effect of PEI on ATNs can be evaluated with an MR examination that is not very time consuming.     

Quantification of Choline-containing Compounds in Malignant Breast Tumors by 1H MR Spectroscopy Using Water as an Internal Reference at 1.5 T

The quantification of choline-containing compounds (Cho) in breast tumors by proton MR spectroscopy (¹H-MRS) has been of great interest because such compounds have been linked to malignancy. In this study, an internal reference method for the absolute quantification of Cho metabolite in malignant breast tumors was presented using a clinical 1.5 T scanner. We performed in vitro measurements to examine the accuracy of absolute quantification using four phantoms of known choline chloride concentrations. There was a high correlation between the calculated concentrations by MRS and the known concentrations (r ² > 0.98). We applied the technique to in vivo breast study conducted on 45 patients with biopsy-confirmed breast cancer. After T ₁ and T ₂ relaxation times were corrected, the Cho levels in this work had a range of 0.76 – 21.20 mmol/kg from 34 MR spectra of 32 patients with malignant breast lesions. This result was rather consistent with the previously published value (i.e., 1.38 – 10 mmol/kg, Bolan et al. in Magn Reson Med 50:1134–1143, 2003). Therefore, we conclude that the internal method using the fully relaxed water as a reference could be used for quantifying Cho metabolite accurately in breast cancer patients using a clinical 1.5 T scanner.     

PZT thick films by diol chemical solution deposition

Process optimization and properties of lead zirconate titanate (PZT) films for piezoelectric micromachined ultrasonic transducers (pMUTs) for scanning probe devices will be presented. The goal of the work was a replacement of the tetragenic and mutagenic solvent and a decrease of time-consuming PZT 2–methoxy ethanol (2MOE) route. An alternative diol-based solution synthesis process was developed and “Design Of Experiment” (DOE) was used to achieve processing optimization for thick and crack free films. Tight parameter control allowed to develop a highly reproducible PZT diol process. The crystallization behaviour of crack-free PbZr_0.53Ti_0.47O₃ films (1–5 μm) with oriented perovskite structure was examined by X-ray diffraction and surface analysis using scanning electron microscopy. Piezoelectric and dielectric properties were examined. The effective transverse piezoelectric coefficient e _31,f of sol–gel processed films was investigated for 4 μm thick layers. Best properties were achieved with {1 0 0}-textured films, where a remanent e _31,f value of −7.3 C/m² was measured for 4.1 μm thick films.     

Analytical delay models for RLC interconnects under ramp input

Analytical delay models for Resistance Inductance Capacitance (RLC) interconnects with ramp input are presented for different situations, which include overdamped, underdamped and critical response cases. The errors of delay estimation using the analytical models proposed in this paper are less by 3% in comparison to the SPICE-computed delay. These models are meaningful for the delay analysis of actual circuits in which the input signal is ramp but not ideal step input. Translated from Journal of Shanghai Jiaotong University, 2006, 40(3): 373–376 [译自: 上海交通大学学报]     

Zeolite coating on foamed stainless steel by in-situ crystallization method

Faujasite-type zeolite films were prepared on foamed stainless steel by the in-situ crystallization method. Precursor solutions were prepared by dissolving water glass and NaAlO₂in a NaOH solution and aged at room temperature for two days. The concentrations of the starting materials were varied from 0.29 to 2.3 M (in SiO₂concentration) keeping the molar ratios of Na₂O:SiO₂:Al₂O₃fixed at 3.6:3.0:1.0. The foamed stainless steel substrate had about 90% of porosity and an average pore size of 600 μ m. It was dip-coated in the precursor solution four times, then hydrothermally treated at 80^∘, 110^∘ and 150^∘C for 6–48 h. The XRD patterns and SEM photographs revealed that faujasite-type zeolite was formed predominantly at a SiO₂concentration of 1.1 M, temperature of 110^∘C and duration of 24 h, with a product particle size of 2–5 μ m. At higher concentrations of the precursor solution, hydroxylsodalite becomes the major product rather than faujasite-type zeolite. The adherence strength of the zeolite grains deposited on the foamed stainless steel is higher in the in-situ crystallization method than when a conventional solution method is used. Thus, the in-situ crystallization method is concluded to be effective for preparing zeolite films even on metal substrates.     

A double-blind study to evaluate the efficacy and tolerability of a higher dose (0.3 mmol per kg bw) of gadodiamide injection as a contrast medium for MRI

Gadodiamide injection was administered intravenously to 48 patients with known or suspected central nervous system (CNS) lesions undergoing magnetic resonance imaging (MRI). Two parallel groups were examined to evaluate the efficacy and safety of single doses of 0.1 and 0.3mmol per kg bw. The principal measures of efficacy were diagnostic yield of MR images, the overall contrast enhancement and the contrast index (CI). Adverse events and serum bilirubin level were the main safety parameters. Nineteen patients in each dose group displayed contrast enhancement of the MR image (1.5 T Siemens Gyroscan MR unit;T ₁ TR/TE=560–650/15–25 ms;T ₂:TR/TE=2200–3100/22–90 ms). The CI increased by 47.3% in the 0.1 mmol/kg bw group and by 86.5% in the 0.3 mmol per kg bw group compared to the pre-contrast scan. Four patients in the 0.1 mmol per kg bw group and seven in the 0.3 mmol per kg bw group had their management changed by new information from the post-contrast scan and four patients in each dose group had their diagnosis altered following the post-contrast scan. Two patients in the 0.3 mmol per kg bw group experienced injection-associated discomfort. There were no other adverse events reported during the 24 h follow-up period. No clinically significant changes in serum bilirubin or other parameters of blood chemistry or haematology were observed. The study demonstrates that the safety profile of gadodiamide injection 0.3 mmol per kg bw is similar to that of 0.1 mmol per kg bw and that, at both doses, gadodiamide injection is a safe and effective contrast medium for use in patients undergoing MRI on the CNS. Slightly more patients had an improvement in diagnostic yield with the 0.3 mmol per kg bw dose and the CI was increased to a greater extent in this group, showing that when greater contrast is required the higher dose of gadodiamide injection may be considered. Further studies in selected patient groups, and with the use of different doses in the same patient are necessary to evaluate the diagnostic value of higher doses.     

Growth and magnetic properties of Mn and MnSn-doped ZnO nanorods

ZnO nanorods synthesized at 700^∘C by heating the mixture of solution processed Zn precursor with NaCl−Li₂CO₃ salt were examined. The size of the nanorods was in the range of 15–100 nm in diameter and 0.5–5 μm in length. The nanorods show the single crystal structure being free from second phases. The Mn and MnSn-doped nanorods by demonstrated ferromagnetic properties and unique luminescence properties due to doping and charge carrier confinement effects. Magnetic susceptibility of the samples as a function of temperature shows Curie–Weiss behavior. Hysteresis with the coercive field <200 Oe was clearly observed in magnetization versus field curves at 5 and 300 K. Increasing the Mn concentration increases significantly the magnetic hysteresis.     

Analysis of band gap of non-bravais lattice photonic crystal fiber

This article designs a novel type of non-bravais lattice photonic crystal fiber. To form the nesting complexperiod with positive and negative refractive index materials respectively, a cylinder with the same radius and negative refractive index is introduced into the center of each lattice unit cell in the traditional square lattice air-holes photonic crystal fiber. The photonic band-gap of the photonic crystal fiber is calculated numerically by the plane wave expansion method. The result shows that compared with the traditional square photonic band-gap fiber (PBGF), when R/Λ is 0.35, the refractive index of the substrate, airhole, and medium-column are 1.30, 1.0, and −1:0, respectively. This new PBGF can transmit signal by the photonic band-gap effect. When the lattice constant Λ varies from 1:5 μm to 3:0 μm, the range of the wavelength ranges from 880 nm to 2300 nm. __________ Translated from Optoelectronic Technology, 2007, 27(4): 257–260 [译自: 光电子技术]     

Fabrication,property and application of novel pyroelectric single crystals—PMN–PT

The pyroelectric properties and temperature stability of Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃(PMN–xPT) single crystals (0.13 ≤ × ≤ 0.40) were investigated. The best choice for pyroelectric performance is [111]-oriented PMN–0.26PT single crystal whose figures of merit for voltage responsivity and detectivity are 0.11 m²/C and 15 × 10⁻⁵ Pa^−1/2, respectively. However, the [001]-oriented PMN–0.37PT single crystal has much better temperature stability, whose temperature coefficient of pyroelectric property is 0.5%/K in the range of 20 °C to 55 °C, and Curie temperature is high: 175 °C. We also found that PMN–xPT possessed low thermal diffusivity D ~ 4.4 × 10⁻⁷ m²/s, low volume specific heat C _v~ 2.5 × 10⁶ J/m³ K and tunable permittivity ε ~ (300–7000). The pyroelectric performances of PMN–xPT single crystals are superior to those of conventional pyroelectric materials and promising for IR device applications.     

Preparation and Characterization of PZT films Fabricated on Si Substrate

Lead zirconium titanate (PZT) films (Zr/Ti=45:55) with a high dielectric constant are prepared successfully on the low-resistance Si substrate in sol–gel dip-coating process with PT film used as the buffer layer. The dielectric and ferroelectric properties of the films as well as the relationship between crystallization and preparing condition are studied. It is shown that the PZT ferroelectric thin films with a (110) preferred orientation and a well-crystallized perovskite structure could be obtained after annealing at 800°C for 15 min. The particle size of the sample is about 14–25 nm. The P–E hysteresis loops are measured by means of the Sawyer-Tower test system with a compensation resistor at room temperature. The remanent polarization (P _r) and coercive electric field (E _c) of the measured PZT thin films are 47.7 μC/cm² and 18 kV/cm, respectively. The relative dielectric constant ε _r and the dissipation factor tgδ of the PZT thin films were measured with an LCR meter and were found to be 158 and 0.04–0.005, respectively. Translated from “Preparation and Characterization of PZT Films Fabricated on Si Substrates” published in Chinese Journal of Semiconductors, 2004, 25(4): 404–409 (in Chinese)     

Ni-Zn ferrite films synthesized from aqueous solution usable for sheet-type conducted noise suppressors in GHz range

Ni_0.2Zn_0.3Fe_2.5O₄ films (1–5 μm thick) were deposited by spin spray ferrite plating from an aqueous solutions onto polyimide sheets at 90^∘C. Their peel test and high-frequency permeability as well as noise suppression effects were investigated. The oxygen plasma treatment on polyimide sheet surface improved the film adhesion. There was not visible crack on the bended film surface for the Ni-Zn ferrite film thinner than 2 μm and was not peeled off even after the bending test of a million times. The films exhibited excellent high-frequency permeability profile and a natural resonance frequency (where the imaginary permeability reaches a maximum) f _r was 370 ± 30 MHz. The transmission loss increased with the film thickness, reaching the maximum Δ P _loss = 70% at 8 GHz for the 5 μm-thick film. The reflection loss in the measured frequency range was S ₁₁ < 10 % which is small enough for films to be used as the conducted noise suppressors. The value of Δ P _loss obtained for the 5-μm thick film was about 15% higher than that (Δ P _loss = 55 %) attained by the commercialized 50-μm thick noise suppressing sheet.     

Simulation study on delay of end-to-end data communication for protective relaying in substations

The end-to-end delay of protective relaying data flow in a substation was studied by dynamic simulation modeling technology. The distribution characteristics of protective relaying data flow and the constitution of the end-to-end delay of messages were analyzed. The simulation model for digital communication between protective relaying equipment and monitoring equipment of interval layer was suggested. The end-to-end delay of protective relaying data flow in different network configurations was analyzed. It is found that the size and interval of the data frame, utilization of the link background and protocols of higher layer are key factors of real-time performance. Detailed analysis results are presented. A proposal for network configuration is suggested to reduce end-to-end delay of protective relaying data flow. __________ Translated from Journal of North China Electric Power University, 2007, 34(1): 101–105 [译自: 华北电力大学学报]     

Validation of glutathione quantitation from STEAM spectra against edited 1H NMR spectroscopy at 4T: application to schizophrenia

Objective: Quantitation of glutathione (GSH) in the human brain in vivo using short echo time ¹ H NMR spectroscopy is challenging because GSH resonances are not easily resolved. The main objective of this study was to validate such quantitation in a clinically relevant population using the resolved GSH resonances provided by edited spectroscopy. A secondary objective was to compare several of the neurochemical concentrations quantified along with GSH using LCModel analysis of short echo time spectra in schizophrenia versus control. Materials and Methods: GSH was quantified at 4T from short echo STEAM spectra and MEGA-PRESS edited spectra from identical volumes of interest (anterior cingulate) in ten volunteers. Neurochemical profiles were quantified in nine controls and 13 medicated schizophrenic patients. Results: GSH concentrations as quantified using STEAM, 1.6 ± 0.4 μmol/g (mean ± SD, n=10), were within error of those quantified using edited spectra, 1.4 ± 0.4 μmol/g, and were not different (p=0.4). None of the neurochemical measurements reached sufficient statistical power to detect differences smaller than 10% in schizophrenia versus control. As such, no differences were observed. Conclusions: Human brain GSH concentrations can be quantified in a clinical setting using short-echo time STEAM spectra at 4T.     

Delay-dependent robust H ∞ controller design for a class of nonlinear uncertainty time-delay systems with input delay

Based on an appropriate Lyapunov function, this paper analyzes the design of a delay-dependent robust H _∞ state feedback control, with a focus on a class of nonlinear uncertainty linear time-delay systems with input delay using linear matrix inequalities. Under the condition that the nonlinear uncertain functions are gain bounded, a sufficient condition dependent on the delays of the state and input is presented for the existence of H _∞ controller. The proposed controller not only stabilized closed-loop uncertain systems but also guaranteed a prescribed H _∞ norm bound of closed-loop transfer matrix from the disturbance to controlled output. By solving a linear matrix inequation, we can obtain the robust H _∞ controller. An example is given to show the effectiveness of the proposed method. __________ Translated from Journal of Nanjing University of Aeronautics and Astronautics, 2007, 39(2): 159–163 [译自: 南京航空航天大学学报]