Light-induced color changes and chemical modification of treated and untreated chestnut wood surface     

none 《文物保护研究》2013,58(2):131-139

Abstract

The aim of this work is to study the surface modifications of chestnut (Castanea sativa Mill.) wood by reflectance spectrophotometry and Fourier transform infrared spectroscopy (FTIR) in order to understand the mechanisms that cause changes and to suggest possible solutions to avoid degradation phenomena. The experimental data were statistically treated to evaluate their significance. Concerning the surface protection of wood, starting from the results obtained by testing different commercial products, attention was focused on a novel organic preservative/consolidant product (Linfoil^®) that has attracted great interest in the field of conservation of wooden artifacts. Color monitoring showed that wood surface color undergoes an important variation due to photoirradiation, occurring within the first 24 hours and mainly due to L* decrease and b* increase. Though the protective treatment modifies wood color, nevertheless the product tested seems to protect the wood surface by reducing photoyellowing. FTIR analysis indicated that irradiation caused the degradation of lignin and increased the concentration of the chromophore groups on the wood surface. Changes in the chromaticity coordinates can be linked to the degradation of lignin and to increase of the concentration of carbonyl groups.  相似文献   

Effect of pH on spectral characteristics of P5C-ninhydrin derivative: Application in the assay of ornithine amino transferase activity from tissue lysate     

H. Ravikumar  K. S. Devaraju  K. Taranath Shetty 《Indian journal of clinical biochemistry : IJCB》2008,23(2):117-122

Currently available method(s) for assaying pyrroline-5-carboxylate (P5C), an important intermediate metabolite of ornithine, proline and glutamate metabolic pathways, are cumbersome or not sensitive enough for microanalysis. The present study involving the synthesis of P5C followed by purity check, molecular mass (amu =113.1) determination by mass spectrometry and spectral characterization of P5C-ninhydrin derivative (λ max: 510 nm) confirmed the authenticity of the preparation. Studies on the effect of pH on spectral characteristics of P5C ninhydrin derivative demonstrated a significant change with respect to λ max (620 nm) and several ∼ 12 fold increase in molar extinction coefficient (ε: 1.96 × 10⁵) in alkaline conditions (pH:7.0–8.0) as compared to the reported Molar ε of 1.65 × 10⁴ at max λ 510 nm in ethanolic solution. The modified method, with the improved sensitivity, is adopted for the assay of ornithine amino transferase activity in WBC’s/platelets lysate(s) from human blood.  相似文献   

氧化镁和氧化钇掺杂对纳米氧化铝粉末的影响     

廖树帜  徐仲榆  张邦维  舒小林  欧阳义芳  谢浩文  王玲玲 《湖南师范大学教育科学学报》1998,(5)

本文研究了用均相共沉淀法合成氧化铝陶瓷粉末的同时合成氧化镁、氧化钇等掺杂氧化物,发现在掺杂量不大时,同时合成的掺杂氧化物以填隙固溶体方式固溶于立方γ氧化铝中,并且几乎不影响铝氧键性质、晶格常数和衍射波矢,但掺杂使氧化物细化,比表面增大,用此法合成的粉末聚集比较厉害,在粉末中有晶化颗粒存在．  相似文献   

The effects of 4 weeks normobaric hypoxia training on microvascular responses in the forearm flexor     

S. Fryer  K. Stone  T. Dickson  A. Wilhelmsen  D. Cowen  J. Faulkner 《Journal of sports sciences》2019,37(11):1235-1241

Intermittent exposure to hypoxia can lead to improved endurance performance. Currently, it is unclear whether peripheral adaptions play a role in improving oxygen delivery and utilization following both training and detraining. This study aimed to characterize skeletal muscle blood flow (mBF), oxygen consumption (mV?O₂), and perfusion adaptations to i) 4-weeks handgrip training in hypoxic and normoxic conditions, and ii) following 4-weeks detraining. Using a randomised crossover design, 9 males completed 30-min handgrip training four times a week in hypoxic (14% FiO₂ ~ 3250m altitude) and normoxic conditions. mBF, mV?O₂ and perfusion were assessed pre, post 4-weeks training, and following 4-weeks detraining. Hierarchical linear modelling found that mV?O₂ increased at a significantly faster rate (58%) with hypoxic training (0.09 mlO₂·min^?1 · 100g^?1 per week); perfusion increased at a significantly (69%) faster rate with hypoxic training (3.72 μM per week). mBF did not significantly change for the normoxic condition, but there was a significant increase of 0.38 ml· min^?1 · 100ml^?1 per week (95% CI: 0.35, 0.40) for the hypoxic condition. During 4-weeks detraining, mV?O₂ and perfusion significantly declined at similar rates for both conditions, whereas mBF decreased significantly faster following hypoxic training. Four weeks hypoxic training increases the delivery and utilisation of oxygen in the periphery.  相似文献   

FTIR Measurement of Cellulose Microfibril Angle in Historic Scots Pine Wood and Its Use to Detect Fungal Decay     

Kate Hudson-McAulay  David Auty 《文物保护研究》2018,63(6):375-382

Microfibril angle (MFA) – the orientation of cellulose fibres in the S2 layer of the secondary cell wall – is a key determinant of the stiffness and strength of timber. The microfibril angle depends on the way in which the timber was grown and its position within the tree. Microfibril angle can be measured by X-ray diffraction and other methods, but the methods in current use are slow or require advanced instrumentation. The aim of this study was to explore the use of polarised Fourier transform infrared (FTIR) microscopy as a relatively fast and inexpensive method for measuring MFA in historic Scots pine (Pinus sylvestris L.). The FTIR measurements were calibrated against X-ray measurements of MFA in modern Scots pine. We observed a wide range in MFA values and a radial pattern of MFA similar to modern Scots pine in undecayed Scots pine heartwood from sixteenth and seventeenth century beams in Scottish secular buildings. The density of the heartwood was also similar to modern plantation-grown Scots pine despite the much slower growth rate recorded in the ring widths of the historic timber. The sapwood, which had been attacked by both insect pests and fungi, showed an erratic reduction in density and a large increase in MFA compared to the modern material. The increased sapwood MFA was attributed to selective destruction of the S2 layer of the wood cell walls by fungal decay. Using MFA measurements in conjunction with density offers the possibility to estimate the mechanical properties of sound historic pine timber, to detect fungal decay more sensitively than by density alone, and to distinguish between pest and fungal attack in a way that relates directly to the remaining mechanical performance of the timber.  相似文献   

光电探测系统的设计原理及应用   总被引：2，自引：0，他引：2  

朱立文 《鄂州大学学报》2003,10(4):52-55

该文根据“非典”时期红外测温仪的应用，讨论了光电系统的设计思想和基本原理及应用。  相似文献   

论二正（异）丙氧基-三嗪的合成     

唐皓李宪平  肖新初 《娄底师专学报》2005,(5):33-36

以三聚氯氰为起始原料合成了四种三嗪衍生物,并用红外光谱和质谱分析法对它们进行了表征.产品检测结果表明,四种三嗪衍生物有较高熔点,在常温下不易挥发.  相似文献   

悬浮液进样一火焰原子吸收光谱法测定中草药中的锰     

薛元英  林培喜  陈静  唐永 《茂名学院学报》2001,11(4):10-12

将悬浮液进样－火焰原子吸收光谱法应用于中草药中锰的测定，建立了中草药中锰的快速分析新方法，将样品粉碎，磨细悬浮于琼脂胶体中，直接喷入空气－乙炔，火焰，以空白溶液为参比，用氘灯扣除背景吸收，用标准曲线法测定了泽泻中的锰，测定结果与消化法一致，两种方法的相对误差小于3．6％，RSD小于1．8％,t检验表明两种方法之间无显著性差异，方法简便，快速，准确。  相似文献   

快速检测熏硫银耳系统设计及实验教学应用     

王硕南  王永清  张欣  周颖昌 《教育教学论坛》2019,(7):73-74

银耳被硫磺熏蒸后能够防霉变、防虫蛀,并且鲜艳卖相好。但长期服用熏硫银耳会伤害身体。本项目开发了便携式可见-近红外光谱法快速检测硫熏银耳测试系统,通过对熏硫银耳样品的实验测试结果,得到熏硫银耳中残留的硫磺在715 nm和835 nm处存在明显吸收峰,说明银耳含有硫磺残留,实现了熏硫银耳中硫磺残留量的快速检测。有助于市场现场鉴别熏硫银耳,为加强市场管理提高了有效检测方法。将研究结果用于传感器等课程实验教学后,激发了学生的学习兴趣,有助于工科学生实践创新能力的培养。  相似文献   

电教设备中央控制系统的设计     

陈丹 《中国教育技术装备》2003,(3):12-15

阐述了为在一个综合控制平台上对各种多媒体设备及灯光、窗帘，摄像机的运作实行遥控，如何利用分布式单片机控制技术，PC机串行通信技术，红外二次调制编码遥控等技术，进行硬件，软件的设计，分析了它们的原理及实现手段。  相似文献