Extracellular recordings from patterned neuronal networks using planar microelectrode arrays

Neuronal cell networks have been reconstructed on planar microelectrode arrays (MEAs) from dissociated hippocampal pyramidal neurons. Microcontact printing (microCP) and a photoresist-liftoff method were used to selectively localize poly-L-lysine (PLL) on the surface of MEAs. Haptotaxis led to the organization of the neurons into networks localized adjacent to microelectrodes. Various grids of PLL with 2-25-microm-wide lines spaced by 50-200 microm with 15-25-microm nodes at intersection points were used to guide cell body attachment and neurite outgrowth. Bursting activity with spike amplitude attenuation was observed, and multichannel recordings detected instances of coincident firing activity. Finally, we present here an extracellular recording from a approximately 2 microm bundle of guided neurites.     

Microstructure coarsening during static annealing of 60Sn40Pb solder joints: II eutectic coarsening kinetics

The eutectic coarsening kinetics for 60Sn40Pb solder joints annealed at 50°C to 150° C was determined to be of the form

复杂RF环境下的RFID测试挑战

亚微米互补金属氧化物半导体（CMOS）的最新发展,可望进一步扩展RFID技术的应用。高精度供应链管理、无接触POS交易、防伪和资产追踪／监测技术所带来的各项优势,正推动着RFID技术的迅速普及。但是,这种新技术自身也面临着许多测试挑战。本文讨论复杂RFID工作环境中的测试挑战,包括多个阅读器、密集模式环境和预先存在的非RFID信号可能引起的吞吐量和通信问题。     

Bistability of theDX center in GaAs and AlxGa1-xAs,and experimental tests for negativeU of theDX level

We summarize a large body of experimental and theoretical work, especially in Si-doped GaAs and Al _x Ga_1-x As, regarding the bistability of theDX center. There is good evidence that theDX center is just the simple donor, and that each donor can exist in either of two distinct lattice configurations, each with its own spectrum of bound electronic states. Generally, the substitutional configuration binds electrons in shallow hydrogenic states, but many observations also indicate a deep (highly localized) state ofA ₁ symmetry. These states are to be distinguished from bound states of a lattice-distorted configuration, the lowest-lying of which is the deepDX level. The occupation of theDX level in thermal equilibrium with the states of the conduction band can be reasonably well modeled by assuming thatDX is either a one-electron or a two-electron state, and we discuss the reasons for this ambiguity. However, we then show that such thermal equilibrium results are consistent with thermal capture and emission kineticsonly if we assume thatDX is a two-electron state. Our results thus support the model of Chadi and Chang in which the distorted configuration is stabilized by capture of two electrons. In other words, the defect exhibits negative effective correlation energy (negativeU).     

Effect of structural parameters on InGaAs/InAlAs 2DEG transport characteristics

The effect of structural parameters on the transport characteristics from 15 to 300 K of molecular beam epitaxy-grown InGaAs/InAlAs two dimensional electron gas structures lattice-matched to InP is determined. The InAlAs buffer layer thickness was varied from 1000 to 10,000Å. One sample also incorporated a InGaAs/InAlAs superlattice. The buffer layer thickness and structure had almost no effect on the mobility or sheet density. The InAlAs spacer layer was varied from 25 to 200Å. Increases in the InAlAs spacer thickness resulted in a monotonically decreasing sheet density and a peak in the mobility versus spacer thickness at 100Å. The highest 77 K mobility was 66,700 cm²/V/sds withN _D =1.2×10¹² cm^?2. The effect of illumination and temperature on the sheet concentration in these structures as well as on “bulk” InAlAs:Si was much smaller than in Al _x Ga_1?x As/GaAs structures or “bulk” Al _x Ga_1?x As, forx?0.30, indicating that devices based on this material system will not be characterized by many of the device instabilities observed in the AlGaAs/GaAs system.     

Heterodyne radiometry measurements of the 557 GHz H2O rotational line

A high-resolution heterodyne radiometer that utilizes a crossed-guide harmonic mixer pumped by a 300 GHz carcinotron as a local oscillator has been developed for submillimeter wavelengths. Previous investigations of the radiation transfer properties of spectral lines in supersonic gas flow have been extended to longer wavelengths using the tunability of this system. With less than 2 mW of fundamental local oscillator power, traces of the 557 GHz ortho-H2O rotational transition (1_{10} leftarrow 1_{01}), Doppler-broadened to only a few MHz, were observed in absorption against a continuum background.     

Microstructure coarsening during static annealing of 60Sn40Pb solder joints: III intermetallic compound growth kientics

The growth of the total (Cu₃Sn+Cu₆Sn) intermetallic compound layer in Cu-60Sn40Pb solder joints during static annealing at 50°C to 150°C was described by the equation hi=h_o+A_o exp(−Q_a/RT)t^p with h_o=0–0.3 μm, p=0.38–0.70, A_o=1.9×10⁻⁴–3.4×10⁻⁴ m/s^p, and Q_a=25.5–30.9 kJ/mole. These constants are within the range of those obtained by others and give values of D_o and Q which are in reasonable accord with those for the diffusion coefficients in Cu₃Sn and Cu₆Sn₅ determined in diffusion couples. The deviation of the values of the time exponent p from the ideal of 0.5 for diffusion growth may be due to inaccuracies or errors pertaining to the measured thickness (especially h_o) and the complex nature of the diffusion process.     

Myoelectric signal classification for phoneme-based speech recognition

Traditional acoustic speech recognition accuracies have been shown to deteriorate in highly noisy environments. A secondary information source is exploited using surface myoelectric signals (MES) collected from facial articulatory muscles during speech. Words are classified at the phoneme level using a hidden Markov model (HMM) classifier. Acoustic and MES data was collected while the words "zero" through "nine" were spoken. An acoustic expert classified the 18 formative phonemes in low noise levels [signal-to-noise ratio (SNR) of 17.5 dB] with an accuracy of 99%, but deteriorated to approximately 38% under simulations with SNR approaching 0 dB. A fused acoustic-myoelectric multiexpert system, without knowledge of SNR, improved on acoustic classification results at all noise levels. A multiexpert system, incorporating SNR information, obtained accuracies of 99% at low noise levels while maintaining accuracies above 94% during low SNR (0 dB) simulations. Results improve on previous full word MES speech recognition accuracies by almost 10%.     

Growth of CdTe Films on Amorphous Substrates Using CaF<Subscript>2</Subscript> Nanorods as a Buffer Layer

Continuous biaxially textured CdTe films were grown on biaxial CaF₂ buffer layers. The CaF₂ nanorods were grown by oblique angle vapor deposition and possessed a {111} 〈121〉 biaxial texture. The CdTe film was deposited by metal organic chemical vapor deposition (MOCVD). Film morphology and the CdTe/CaF₂ interface were studied by scanning electron microscopy and transmission electron microscopy. Characterization showed that small CdTe grains formed initially from the CaF₂ surfaces. These small grains then merged into large columnar grains during growth. Analysis revealed that the crystalline orientation of the CdTe film followed the biaxial texture of the CaF₂ nanorods.     

Milk fever in dairy cows. VIII. Effect of injected vitamin D3 and calcium and phosphorus intake on incidence.

In a field trial, effects of prepartal intermuscular injection of 10 million units of vitamin D3 on incidence of milk fever were examined both in relation to intake of calcium and phosphorous during the dry period and previous history of milk fever. Based upon intake of calcium and phosphorus cooperating herds were grouped as feeding: 1) greater than .53% of the total ration dry matter as calcium and greater than .28% as phosphorus: 2) less than .47% as calcium and greater than .28% as phosphorus; 3) greater than .47% to less than .53% as calcium and greater than .22% to less than .28% as phosphorus. Injections of vitamin D3 given approximately 1 wk prepartum reduced incidence of milk fever in cows with previous history of milk fever in all three groups but had no effect in cows with no previous milk fever. Incidence of milk fever was lower in group 3 than for cows of groups 1 and 2 with previous milk fever and than for cows of group 1 with no previous history. The results indicate that careful control of calcium and phosphorus intake during the dry period at .5% calcium and .25% phosphorus of the dry matter of the total ration will limit milk fever incidence to about 10%. Injections of vitamin D3 as described will reduce inicidence of milk fever further in cows with previous milk fever but not in cows with no previous milk fever.