Identification of the veratryl alcohol binding site in lignin peroxidase by site-directed mutagenesis

Site-directed mutagenesis was used to identify the veratryl alcohol binding site of lignin peroxidase. The cDNA encoding isozyme H8 was mutated at Glu146 to both an Ala and a Ser residue. The H8 polypeptide was produced by E. coli as inclusion bodies and refolded to yield active enzyme. The wild type recombinant enzyme and the mutants were purified to homogeneity and characterized by steady state kinetics. The kcat is decreased for both mutants of Glu146. The reactivity of mutants (kcat/Km) toward H2O2 were not affected. In contrast, the kcat/Km of the mutants for veratryl alcohol were decreased by at least half. The oxidation of guaiacol by these mutants were more significantly affected. These results collectively suggest that E146 plays a central role in the binding of veratryl alcohol by lignin peroxidase.     

梳齿的不平行对电容式微机械传感器阶跃信号响应的影响

分析了梳齿电容式传感器在三种电容驱动方式下,梳齿电容极板的不平行对传感器受到阶跃加速度信号作用时可靠工作条件的影响。得到了梳齿倾斜效应对传感器阶跃加速度响应影响的分析模型。结果表明梳齿电容在同样的电压驱动下,若电容极板的倾斜角变到0.5°时,对于单边电容结构、双边电容结构和有力反馈的双边电容结构,传感器能够承受的临界阶跃加速度分别变为电容极板完全平行时的0.34、0.44、0.52。并针对DRIE工艺刻蚀梳齿的原理,讨论了改进梳齿不平行的方法。     

Continuous-wave operation of 5 /spl mu/m quantum cascade lasers with high-reflection coated facets

A report is presented on the continuous-wave operation of /spl lambda//spl sime/5 /spl mu/m GaInAs/AlInAs/InP-based quantum cascade lasers up to a heatsink temperature of 222 K (-51/spl deg/C). The devices are mounted epi-side down with high-reflection coated facets. The dissipated electrical power at threshold amounts to only 2.3 W at 222 K.     

256×256 focal plane array midwavelength infrared camera based on InAs/GaSb short-period superlattices

An infrared camera based on a 256×256 focal plane array (FPA) for the second atmospheric window (3–5 μm) has been realized for the first time with InAs/GaSb short period superlattices (SLs). The SL detector structure with a broken gap type-II band alignment was grown by molecular beam epitaxy on GaSb substrates. Effective bandgap and strain in the superlattice were adjusted by varying the thickness of the InAs and GaSb layers and the controlled formation of InSb-like bonds at the interfaces. The FPAs were processed in a full wafer process using optical lithography, chemical-assisted ion beam etching, and conventional metallization technology. The FPAs were flip-chip bonded using indium solder bumps with a read-out integrated circuit and mounted into an integrated detector cooler assembly. The FPAs with a cut-off wavelength of 5.4 μm exhibit quantum efficiencies of 30% and detectivity values exceeding 10¹³ Jones at T=77 K. A noise equivalent temperature difference (NETD) of 11.1 mK was measured for an integration time of 5 ms using f/2 optics. The NETD scales inversely proportional to the square root of the integration time between 5 ms and 1 ms, revealing background limited performance. Excellent thermal images with low NETD values and a very good modulation transfer function demonstrate the high potential of this material system for the fabrication of future thermal imaging systems.     

Immersive electronic books for surgical training

Immersive electronic books (IEBooks) for surgical training will let surgeons explore previous surgical procedures in 3D. The authors describe the techniques and tools for creating a preliminary IEBook, embodying some of the basic concepts.     

Negative and positive luminescence in midwavelength infrared InAs-GaSb superlattice photodiodes

The quantum efficiency of negative and positive luminescence in binary type-II InAs-GaSb superlattice photodiodes has been investigated in the midinfrared spectral range around the 5-/spl mu/m wavelength. The negative luminescence efficiency is nearly independent on temperature in the entire range from 220 to 325 K. For infrared diodes with a 2-/spl mu/m absorbing layer, processed without anti-reflection coating, a negative luminescence efficiency of 45% is found, indicating very efficient minority carrier extraction. The temperature dependent measurements of the quantum efficiency of the positive luminescence enables for the determination of the capture cross section of the Shockley-Read-Hall centers involved in the competing nonradiative recombination.     

一种中频接收电路的版图设计

利用Cadence版图设计工具采用B300工艺对一种中频接收电路芯片的版图设计实例,阐述了模拟集成电路版图的设计过程,论述了包括单元库建立、布局、布线、设计规则检查（DRC）和版图对照原理图检查（LVS）等在内的设计步骤以及进行每一步骤的具体方法,尤其对布局和布线这样的关键步骤进行了重点讨论。最后给出了完整的芯片版图。     

Rectangular Pisarenko method applied to source localization

Most high-resolution (HR) direction-of-arrival (DOA) estimation schemes require the extraction of a low-dimensional subspace: a task that takes O(N³) flops for an order S matrix. Different techniques have been recently proposed to reduce this computational load. For those working on blocks of data, the number of flops required is generally O(N²P), where P, which is the dimension of the subspace (the number of sources), is often quite small as compared with N, which is the number of sensors. The method we propose is a HR technique that requires O(NP²)+O(P³) flops, i.e., that is linear in the number of sensors. The price to be paid for this drastic computational saving is a reduction in performance. Although the Cramer-Rao lower bound (CRLB) on the variance of the direction estimates is of the order T^-1 N^-3 (with T the number of snapshots), this variance is of order T^-1 N^-2 for the proposed procedure. The idea behind the method is to apply a Pisarenko method to a rectangular matrix extracted from the Toeplerized estimated covariance matrix, and it is this Toeplerization that allows preservation of the O(T^-1 N^-2) level of performance     

Understanding movement data quality

Abstract

Understanding of data quality is essential for choosing suitable analysis methods and interpreting their results. Investigation of quality of movement data, due to their spatio-temporal nature, requires consideration from multiple perspectives at different scales. We review the key properties of movement data and, on their basis, create a typology of possible data quality problems and suggest approaches to identify these types of problems.     

新型隔热和导电防护服综述

介绍了隔热导电防护服的市场状况及发展趋势、新型防护服的标准和需求分布,隔热导电防护服的测试方法。