In vivo PIXE-PIGE study of enhanced retention of fluorine in tooth enamel after laser irradiation

The presence of fluoride in tooth enamel reduces the solubility of hydroxylapatite by acid attack. Fluoride presence (even at low concentration) in the oral cavity is efficient against caries process. We propose a new approach of the explanation of the increase of fluoride retention in the tooth enamel when low power laser irradiation is applied after the treatment with fluoride gel (fluoridation). External beam PIGE measurements of fluorine on extracted teeth have been made in order to determine the best sequence of the operations. The laser irradiation after fluoride application is more efficient than the reverse procedure. This observation is in agreement with previous observations that the fluorine penetration in the enamel takes place first in the soft organic material present between the polycrystalline (prismatic) structure before being integrated in the crystalline composition of hydroxylapatite in order to produce fluoro-apatite. As those in vitro measurements do not reflect the whole process in the saliva, in vivo PIGE measurements have been also performed. We have demonstrated, by repeating the PIGE measurements (at least five times at various time intervals) that a significant increase of the fluoride retention took place even 18 months after the unique laser treatment. The complete experimental procedure is described: fluoride application, laser irradiation, PIGE measurements with 2.7 MeV protons (repeated measurements at the same place on the same tooth in order to follow the evolution) and safety tests before in vivo analyses.     

基于nRf2401和CP2102的USB2.0无线测控网络

本系统使用nRf2401和CP2102实现PC-USB2.0-MCU高速无线测控网络.系统通过CP2102实现USB2.0接口,通过nRF2401实现无线数据收发.同时nRf2401厂商免费提供驱动程序,开发方便、快速.本文阐述该系统的工作原理、硬件构成及软件设计方案.     

Quantification of sodium in ancient Roman glasses with ion beam analysis

Concentrations of light elements (Na, Al, Si) in glass have been profiled by comparing the PIGE yields as a function of beam energy to those of a glass standard in combination with PIXE measurements which are used to determine the specific energy loss of protons in the unknown glasses. The technique has been tested on a known sample and applied to a few Roman natron glasses giving results compatible with the morphology of the archaeological samples, as deduced from microscopy. The results have suggested some considerations on the systematic use of the PIGE technique in the determination of bulk sodium concentration in ancient materials.     

The sensitivity of the PIGE analytical technique

The aim of this work is to provide a basis for the estimation of fluorine and lithium contributions to the background of gamma-ray spectra and of their influence on PIGE (Proton-Induced Gamma-Ray Emission) detection limits of lithium, boron, fluorine and sodium. Results for yields and background contributions of lithium and fluorine were obtained from measurements using samples of known composition. Detection limits were determined by extrapolation of those measurements and by calculations based on the inferred background values. Yields were converted in concentrations using the ERYA (Emitted Radiation Yield Analysis) code. This code divides the sample in sublayers parallel to its surface for the integration of the partial gamma-ray yields along the depth of the target.     

TRIAC II. A MatLab code for track measurements from SSNT detectors

A computer program named TRIAC II written in MATLAB and running with a friendly GUI has been developed for recognition and parameters measurements of particles' tracks from images of Solid State Nuclear Track Detectors. The program, using image analysis tools, counts the number of tracks and depending on the current working mode classifies them according to their radii (Mode I—circular tracks) or their axis (Mode II—elliptical tracks), their mean intensity value (brightness) and their orientation. Images of the detectors' surfaces are input to the code, which generates text files as output, including the number of counted tracks with the associated track parameters. Hough transform techniques are used for the estimation of the number of tracks and their parameters, providing results even in cases of overlapping tracks. Finally, it is possible for the user to obtain informative histograms as well as output files for each image and/or group of images.

Program summary

Title of program:TRIAC IICatalogue identifier:ADZC_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADZC_v1_0Program obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandComputer: Pentium III, 600 MHzInstallations: MATLAB 7.0Operating system under which the program has been tested: Windows XPProgramming language used:MATLABMemory required to execute with typical data:256 MBNo. of bits in a word:32No. of processors used:oneHas the code been vectorized or parallelized?:noNo. of lines in distributed program, including test data, etc.:25 964No. of bytes in distributed program including test data, etc.: 4 354 510Distribution format:tar.gzAdditional comments: This program requires the MatLab Statistical toolbox and the Image Processing Toolbox to be installed.Nature of physical problem: Following the passage of a charged particle (protons and heavier) through a Solid State Nuclear Track Detector (SSNTD), a damage region is created, usually named latent track. After the chemical etching of the detectors in aqueous NaOH or KOH solutions, latent tracks can be sufficiently enlarged (with diameters of 1 μm or more) to become visible under an optical microscope. Using the appropriate apparatus, one can record images of the SSNTD's surface. The shapes of the particle's tracks are strongly dependent on their charge, energy and the angle of incidence. Generally, they have elliptical shapes and in the special case of vertical incidence, they are circular. The manual counting of tracks is a tedious and time-consuming task. An automatic system is needed to speed up the process and to increase the accuracy of the results.Method of solution: TRIAC II is based on a segmentation method that groups image pixels according to their intensity value (brightness) in a number of grey level groups. After the segmentation of pixels, the program recognizes and separates the track from the background, subsequently performing image morphology, where oversized objects or objects smaller than a threshold value are removed. Finally, using the appropriate Hough transform technique, the program counts the tracks, even those which overlap and classifies them according to their shape parameters and brightness.Typical running time: The analysis of an image with a PC (Intel Pentium III processor running at 600 MHz) requires 2 to 10 minutes, depending on the number of observed tracks and the digital resolution of the image.Unusual features of the program: This program has been tested with images of CR-39 detectors exposed to alpha particles. Also, in low contrast images with few or small tracks, background pixels can be recognized as track pixels. To avoid this problem the brightness of the background pixels should be sufficiently higher than that of the track pixels.     

MATLAB在选煤中的应用研究

通过运用MATLAB编写的几个典型的常用选煤数据处理和曲线绘制实例,探索利用MAT-LAB软件处理选煤工艺问题及设备研制的简捷途径。     

用扩频技术改造煤矿井下电力线载波通信试验

根据煤矿井下环境对载波通信的影响,提出基于PL2102芯片的低压电力线载波扩频数据通信系统,可有效地改进煤矿井下电力线载波通信的传输质量.     

RBS, XPS, and TEM study of metal and polymer interface modified by plasma treatment

We performed a study of the diffusion of Ag and Au atoms in polyethyleneterephtalate (PET). Thin metal layers were deposited using a diode-sputtering technique on polymer foils at room temperature. Simultaneous post-deposition annealing and plasma treatments were used to induce metal-polymer intermixing. Rutherford back-scattering spectrometry and X-ray photoelectron spectroscopy were used to determine the integral amount of metal and chemical structure in the surface layer. After plasma treatment Ag thin films exhibit dramatic changes of chemical composition and an integral amount of metal compared to Au thin films. Transmission Electron Microscopy shows the differences in the size and the depth distribution of metal particles, depending on the annealing temperature at the metal-polymer interface.     

无线U盘数据分享系统

利用USB总线接口芯片CH375并结合单片机89S52实现单片机读写u盘,采用无线收发模块nRF24E1构建点对点无线通信系统,并完成通信协议的编写及软件设计,探讨了数据传输过程中差错校验及解决措施。本系统为无线射频通信系统的软硬件设计提供了可行的解决方案。     

USB-UART转换器CP2102在智能电动机保护器中的应用

CP2102是美国Silicon公司推出的USB-UART数据转换器,通过它实现USB2.0到UART的转换。不仅适合设计新一代的带有USB接口的系统,也可以利用它对采用RS-232通信接口的系统进行改造,只需用CP2102取代RS-232电平转换器即可。本文介绍了CP2102主要特性、工作原理及其在智能电动机保护器中的应用,给出了部分原理图和数据流图。通过实验证明CP2102具有功能强大,尺寸小,外围电路简单等优点,取得了较好的应用效果。