Differentiation of apple juice samples on the basis of heat treatment and variety using chemometric analysis of MIR and NIR data

The potential of mid-infrared (MIR) and near-infrared (NIR) spectroscopy for their ability to differentiate between apple juice samples on the basis of apple variety and applied heat-treatment was evaluated. The heat-treatment involved exposure of juice samples (15 ml) for 30 s in a 900 W microwave oven and the apple varieties used to produce the juice samples were Bramley, Elstar, Golden Delicious and Jonagold. The chemometric procedures applied to the MIR and NIR data were partial least squares regression (PLS1 for differentiation on the basis of heat-treatment, PLS2 for varietal differentiation) and linear discriminant analysis (LDA) applied to principal component (PC) scores. PLS1 and PLS2 gave the highest level of correct classification of the apple juice samples according to heat-treatment (77.2% for both MIR and NIR data) and variety (78.3–100% for MIR data; 82.4–100% for NIR data), respectively.     

构成信号发生器的DDS和变换器

许多设备需要使用能产生高性能、高分辩率信号的低频信号发生器.本实例提供一种能产生0～1MHz频率的电路.你利用这种电路就可产生正弦波、三角波和方波,并能达到优于0.1Hz的频率分辨率和优于0.1°的相位分辨率,从而就可以给精确的相干频率编程.这一特点对于数字调制设备和频率调谐设备来说都是很有用的.该电路使用AD μ C381和AD9834来产生所需的频率(图1).利用PC或基于Unix的工作站来给微控制器AD μ C381编程,然后再通过微控制器,利用一个三线串行接口来对AD9834编程.接口的字长为16位.     

多路同步采样ADC实现高性能多通道电网监测

本文介绍了同步采样ADC在电网监测中的应用,并对构建电力线测量系统时所要考虑的问题进行了讨论.     

Fabrication and Optical Properties of Periodic Ag Nano‐Pore and Nano‐Particle Arrays with Controlled Shape and Size over Macroscopic Length Scales

A facile and economical route to preparation of highly ordered sliver pore or particle arrays with controlled pore‐shape and size extended over cm² areas is described. The substrates are prepared at planar and curved surfaces via sphere‐imprinted polymer (PDMS) templating using polystyrene spheres with diameters of 820, 600, or 430 nm. Nano‐pore arrays are created by sputtering 80 nm of Ag directly onto the templates and nano‐particle arrays are prepared by electrode‐less deposition of Ag from Tollen's reagent. The shape of the nano‐pore or particles in the array conformed to that of the imprint of the sphere on the template. Stretching the flexible template enable creation of cuboid shaped nano‐voids and nano‐particles following Ag deposition. Diffuse reflectance from the spherical Ag nano‐cavity arrays showed absorbance maxima at wavelengths comparable similar to the diameter of the templating sphere, whereas reflectance from the cuboid arrays, showed little correlation with the sphere diameter. The cuboid nano‐particle arrays showed the most intense visible absorption which is red‐shifted compared to the spherical arrays. White light diffraction from the arrays, observed by rotating 1 cm² substrates relative to a fixed light source, reflected exactly the symmetry axes of the periodic nano‐features in the arrays demonstrating the remarkable macroscopic order of the periodic structures. Raman spectra of 1‐benzenethiol adsorbed at the arrays indicated SERS enhancements from the substrates are attributed mainly to surface nano‐roughness with only moderate contributions from the periodically corrugated structures. Despite excitation at the major resonance dip in the reflectance spectrum, a weak, localized rim dipole mode is found to elicit a small increase in the SERS enhancement factor for the 430 nm diameter spherical arrays. FDTD studies of nano‐void arrays provided insights into v arious factors affecting the SERS experiment and confirmed the array's plasmonic spectra are dominated by propagating plasmon modes under microscope excitation/collection angles.     

A Study of Saccharomyces cerevisiae Cell Wall Glucans

Much research has been carried out over the years examining cell wall glucans from Saccharomyces cerevisiae and this study further examines aspects of the binding of (1r?4)‐α‐D‐glucan in the yeast cell wall, using a number of isolation techniques as well as monoclonal antibodies able to recognize a mixed (1r?4)‐α‐D‐glucan/(1r?6)‐β‐D‐glucan. Extraction of purified glucan, from S. cerevisiae cell wall, with 0.1N HCl, at 80°C for 6 h, released into the solution (1r?4)‐α‐D‐glucan and (1r?6)‐β‐D‐glucan as the major polysaccharides, along with an insoluble pellet highly enriched in (1r?3)‐β‐D‐glucan. The released (1r?4)‐α‐D‐glucan was composed of a high molecular size >100 kDa fraction (7.2% w/w) and a medium 5–50 kDa polysaccharide (10.2% w/w), with the (1r?4)‐α‐D‐glucan covalently bound to the (1r?6)‐β‐D‐glucan. The average molar ratio of the α:β glucan was 47: 53 in this mixed polysaccharide. The structure of this polysaccharide was different from the structure of plant starch or animal glycogen as monoclonal antibodies specific to yeast (1r?4)‐α‐D‐glucan/(1r?6)‐β‐D‐glucan did not recognize the plant starch or animal glycogen standards.     

Magnetic domain-wall dynamics in a submicrometre ferromagnetic structure

As fabrication technology pushes the dimensions of ferromagnetic structures into the nanoscale, understanding the magnetization processes of these structures is of fundamental interest, and key to future applications in hard disk drives, magnetic random access memory and other 'spintronic' devices. Measurements on elongated magnetic nanostructures highlighted the importance of nucleation and propagation of a magnetic boundary, or domain wall, between opposing magnetic domains in the magnetization reversal process. Domain-wall propagation in confined structures is of basic interest and critical to the performance of a recently demonstrated magnetic logic scheme for spintronics. A previous study of a 500-nm-wide NiFe structure obtained very low domain-wall mobility in a three-layer device. Here we report room-temperature measurements of the propagation velocity of a domain wall in a single-layer planar Ni80Fe20 ferromagnetic nanowire 200 nm wide. The wall velocities are extremely high and, importantly, the intrinsic wall mobility is close to that in continuous films, indicating that lateral confinement does not significantly affect the gyromagnetic spin damping parameter to the extreme extent previously suggested. Consequently the prospects for high-speed domain-wall motion in future nanoscale spintronic devices are excellent.     

Motion planning with inertial constraints

A bodyB must move from a placementZ ₀ to a placementZ ₁, while avoiding collision with a setS of moving obstacles. The motion must satisfy an inertial constraint: the acceleration cannot exceed a given boundM. The problem is analyzed, and polynomial-time motion-planning algorithms are given for the case of a particle moving in one dimension.This work was supported in part by the National Science Foundation under Grant DCR-01898.     

Monitoring hacker activity with a Honeynet

The Honeynet Project was founded by 30 US based security professionals with the intention of researching the techniques, tools, tactics and motives of hackers and the ‘blackhat’ community in general. A Honeynet Project is an all volunteer, non‐profit organization committed to sharing and learning the motives, tools, and tactics of the hacking community. It is comprised of a number of information security professionals dedicated to honeynet research and information security. This paper outlines the technical configuration of a honeynet, presents some of the key attacks on the honeynet to date and provides recommendations for securing networked systems. Copyright © 2005 John Wiley & Sons, Ltd.