一种新型的移动增值服务——动态电话簿

今天的手机采用相对简单的接口就可以进行电话呼叫。虽然相对于传统固定电话拨号略微复杂了一些,但是移动电话接口还是包括了内置电话录和其它崭新的功能。然而,通信远不限于语音通话。现在我们的手机上有文本消息、一键通、图像邮件和多用户游戏。而我们的P C电脑支持即时通信     

Comparison of high-temperature-superconductor and metal-basedresonators

A 50-Ω coplanar waveguide (CPW) resonator designed for a fundamental frequency of about 4.75 GHz was fabricated on LaAlO₃ . Two versions were fabricated: the first using 1.9-μm-thick gold and the second using 0.6-μm-thick YBa₂Cu₃O ₇. The devices were identically packaged and tested at 77 K. It was found that the high-temperature superconductor (HTS) resonator had a surface resistance, R_s, about six to nine times lower than the Au one. At 45 K, the R_s of the HTS resonator decreases by another factor of 4 compared with its 77 K value. Device characteristics for the HTS resonator are presented     

A reexamination of forward masking in the auditory nerve

Forward masking, as measured behaviorally, is defined as an increase in a signal's detection threshold resulting from a preceding masker. Previously, forward masking in the auditory nerve has been measured as a reduction in the neural response to a signal when preceded by a masker. However, detection threshold depends on both the magnitude of the response to the signal and the variance of the response. Thus changes in detectability cannot be inferred from response reduction alone. Relkin and Pelli (1987) have described a two-interval forced-choice procedure that may be used to measure the threshold for the detection of a probe signal in recordings of spike counts in single auditory neurons. These methods have been used to study the forward masking of characteristic frequency probe tones by characteristic frequency maskers as masker intensity was varied. Although the masker does reduce the detectability of the probe tone, it was found that the threshold shifts are much less than those observed behaviorally, particularly for intense maskers. In part, the small threshold shifts can be attributed to the reduction in response variance following the masker, which is the result of the adaptation of spontaneous activity. These results imply that behavioral forward masking must result from suboptimal processing of spike counts from auditory neurons at a location central to the auditory nerve.     

Nonblocking multirate distribution networks

Results for nonblocking distribution networks are generalized for the multirate environment in which different user connections share a switch's internal data paths for arbitrary fractions of the total capacity. Conditions under which network proposed by Y.P. Ofman (1965), C.D. Thompson (1978), and N. Pippenger (1973) lead to multirate distribution networks are derived. The results include both rearrangement and wide-sense nonblocking networks. The complexity of the rearrangement multirate network exceeds that of the corresponding space-division network by a log log factor, while the complexity of the wide-sense nonblocking network is within a factor of two of the corresponding space-division network     

Reactions of the iso-butyl radical during 1,1′-azoisobutane pyrolysis

Quantitative analysis of the products formed in 1,1′-azoisobutane pyrolyses in the temperature range of 553°–602°K has shown that the major reactions of the iso-butyl radical are Analysis of initial rate data gave log₁₀k₄/(k_c)^1/2(cm^?3/2.mol ^1/2.sec^?1/2) = 7.54±0.44 ? (136.5 + 4.8) kJ/mol/2.303RT, the Arrhenius parameters obtained being in good agreement with thermodynamic data for reaction (4). Measured values of k_a/(k_c)^1/2 where k_a is the rate constant of the reaction iC₄H₉ + AIB → iC₄H₁₀ +. AIB were consistent with published parameters determined by photolysis of 1,1′-azoisobutane. Combination of photolysis and pyrolysis data gave log₁₀ k_a/(k_c)^1/2(cm^3/2.mol^?1/22.sec^?1/2) = 3.68 ± 0.15 ? (27.2 ± 1.2) kJ/mol/2.303RT. The crosscombination ratio for methyl and iso-butyl radicals has been found to be 0.25, indicating that the geometric mean rule does not hold for methyl and iso-butyl radicals.     

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.