Role of cellulose oxidation in the yellowing of ancient paper

The yellowing of paper on aging causes major aesthetic damages of cultural heritage. It is due to cellulose oxidation, a complex process with many possible products still to be clarified. By comparing ultraviolet-visible reflectance spectra of ancient and artificially aged modern papers with ab?initio time-dependent density functional theory calculations, we identify and estimate the abundance of oxidized functional groups acting as chromophores and responsible of paper yellowing. This knowledge can be used to set up strategies and selective chemical treatments preventing paper yellowing.     

ToF-SIMS and XPS study of ancient papers

The surface composition of 18th century papers was investigated by means of ToF-SIMS and XPS. The aim of the present study was to explore the possibility of using these surface sensitive methods to obtain information which can help to determine the manufacturing process, provenance and state of conservation of ancient papers. The ToF-SIMS results indicate that the analyzed papers were sized by gelatin and that alum was added as hardening agent. The paper sheets produced in near geographical areas but in different paper mills exhibit a similar surface composition and morphology of the fibers as shown by the ToF-SIMS measurements. The ToF-SIMS and the XPS results indicate that a significant fraction of the cellulose fibers is not covered by the gelatin layer. This was observed for the ancient papers and for a modern handmade paper manufactured according to the old recipes.     

Common black coatings – reflectance and ageing characteristics in the 0.32–14.3 μm wavelength range

The diffuse and regular reflectances of five optically absorbing coatings frequently used in optical systems, were measured over the 0.32–14.3 μm wavelength range, before and after exposure to heat and intense optical radiation. The measured coatings included Nextel Velvet Black, an anodised coating and NPL Super Black. The anodised coating exhibited substantial variations in its diffuse and regular reflectance values after thermal and simulated solar ageing. Solar and thermal ageing of the Nextel Velvet Black resulted in increases of its reflectance. However, thermal ageing tended to decrease the reflectance of the other paint samples examined. Thermal and solar ageing of the NPL Super Black resulted in only minor changes in its reflectance characteristics. All measurements are traceable to the UK National Standards.     

Measurements and analysis of antireflection coatings reflectivity related to external cavity lasers

Facets of semiconductor optical amplifiers (SOA) designed for external cavity lasers must be coated with an antireflection (AR) film of high quality and extremely low reflectance. Therefore measurements of facet reflectance play a crucial role in the fabrication of such AR coating. The reflectance can be estimated by studying the optical power reflected from the Fabry-Perot cavity formed for that purpose by the examined SOA facet and the end of a single-mode fibre. We have made analysis of practical suitability of such measurement method. Theoretical calculations show that, for the low reflectance coatings, losses due to light coupling into optical fibre cannot be omitted in the analysis of the experimental results. To verify this conclusion a theoretical model was tested for a low reflectance surface and we have found that the relative error of the measurements supported by the theoretical model is on the order of 8%.     

Evaluating paper degradation progress. Cross-linking between chromatographic, spectroscopic and chemical results

The study presents an overview of the chromatographic (SEC), spectroscopic (FTIR, UV/VIS), viscometric (DP) and chemical methods (titration, pH) used for the evaluation of the degradation progress of various kinds of paper under various conditions. The methods were chosen to follow different routes of paper degradation. Model paper samples represented boundary paper types from pure cellulose cotton paper, through softwood to low quality acidic, sized groundwood paper The accelerated ageing conditions were adjusted to achieve maximum effect (climatic chamber RH 59%, 90^oC) and also to mimic the environment inside books (closed vials). The results were settled on the literature data on the degradation mechanisms and compared in terms of the paper types and ageing conditions. The estimators of coupled de-polymerisation and oxidation have been proposed based on the correlation between SEC, UV/VIS and titrative coppper number determination. The overall oxidation index derived from FTIR results was shown to correlate with the summary –CHO and –COOH concentration determined by titrative methods.     

Comment on: “growth,spectroscopic studies,and third order non-linear optical analysis of an organic dicarboxylic acid based single crystal: urea oxalic acid” [Chin. J. Phys., 56 (2018) 1449–1466]

In a recent paper [Chin. J. Phys., 56 (2018) 1449–1466] Jeeva et al. have studied the physical properties of the Urea Oxalic acid (UOA) Crystals. The authors have used a wrong approach to calculate the reflectance spectra of the samples and obtained values of this parameter are incorrect. Consequently, other reported optical parameters in the commented paper that are calculated based on the reflectance such as refractive index, real and imaginary parts of the optical dielectric constant, optical and electrical conductivity and electrical susceptibility are incorrect.     

Full field deformation measurement of centimeter sized objects using optical phase retrieval

Most papers in the field of optical phase retrieval either consider only the intensity (or amplitude) profile of the object under inspection (or scatterer location in the X-ray version), or a uniform tilt/rotation of the object beam. However, phase retrieval is able to recover the phase profile of the object (beam) as well, which theoretically makes the observable interference of phase retrieved object waves possible. In this paper we demonstrate this principle experimentally on centimeter sized deformable reflective objects (as large as 40 mm by 40 mm) and corresponding simulations are also presented. When the CCD camera is moved along the optical axis in the Fresnel region, the interference fringes of the displacement field have low contrast. On the other hand, when an imaging setup is built, and the camera moves near the image plane, high fringe contrast can be obtained. These fringes however suffer from some phase error. In our work the iterative modulus projection algorithm was used as a simply implementable phase retrieval method.     

Effect of dilute gelatine on the ultrasonic thermally assisted synthesis of nano hydroxyapatite

A series of nano hydroxyapatite-gelatine composites with different dilute solutions of gelatine concentrations were synthesized by a thermally assisted low-power ultrasonic irradiation method. The gelatine hydroxyapatite, (Gel-HAP) nanoparticles were prepared using Ca(NO(3))(2) and KH(2)PO(4) in the presence of gelatine in an aqueous solution. The synthesised products were heat treated between 100 and 400°C. The effect of the addition of gelatine on the nucleation and growth of synthesised nano HAP was investigated. Characterisation was performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FT-IR). The characterisation results indicate that gelatine has been appended to the nano HAP forming regular spherical shaped crystals of nano sized Gel-HAP.     

光导纤维反射光谱技术在彩绘文物颜料无损分析鉴定中的应用

文物颜料成分分析鉴定是文物材质分析和文物保护工作的重要内容。利用自行研制的光导纤维反射光谱仪对唐代彩绘陶器和壁画上的颜料成分进行了无损分析鉴定,通过比较彩绘文物颜料和标准颜料的反射光谱曲线的形状以及特征峰或一阶导数峰来完成颜料的鉴定工作。光导纤维反射光谱法鉴定出西安市唐代彩绘文物1#样品墓葬壁画上的深红色颜料是纯度较高的土红;2#样品陶器残片上的绿色颜料为石绿;3#样品陶缸残片上的橙红色和朱红色颜料分别是由大量铅丹和微量土红及大量朱砂和微量土红的混合物所组成。采用X射线荧光分析法进行验证,实验结果表明光导纤维反射光谱技术鉴定彩绘文物颜料成分的结果是准确、可靠的,提供了一种文物颜料无损分析的简捷方法。     

Controlled growth of Cu2S hexagonal microdisks and their optical properties

Chalcocite Cu₂S particles have been prepared hydro- and solvo-thermally from a copper plate in pure water, mixed solvents of water and ethylenediamine (en), and pure en, respectively. Their structural and optical properties have been characterized by a combination of powder X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM), and VIS-NIR diffuse reflectance spectroscopy. Their growth and optical properties were found to be highly dependent on synthesis conditions and in particular the en/water volume ratio. For the first time, Cu₂S particles wish the shape of hexagonal microdisks were synthesized in a mild hydrothermal condition and these crystalline particles were found to exhibit unique optical properties.     

Modifications of the mesoscopic structure of cellulose in paper degradation

Paper is the main component of a huge quantity of cultural heritage. It is primarily composed of cellulose that undergoes significant degradation with the passage of time. By using small angle neutron scattering (SANS), we investigated cellulose's supramolecular structure, which allows access to degradation agents, in ancient and modern samples. For the first time, SANS data were interpreted in terms of water-filled pores, with their sizes increasing from 1.61 nm up to 1.97 nm in natural and artificially aged papers. The protective effect of gelatine sizing was also observed.     

颜料层微观形貌对古代壁画褪色及显现影响

文物壁画在自然环境下产生褪色现象具有复杂性,严格意义上讲,人们无法重现自然环境下这种褪色发生的条件,但这并不妨碍人们研究其褪色原因的可能性和途径。通过实验来验证所提出机制的合理性,这也符合自然科学普遍采用的研究方法。提出颜料层微观形貌变化是引起壁画褪色的一种重要原因。胶料作为颜料层的连续相,当胶料分解时,颜料层微观形貌必然产生变化,为证明这种变化会引起颜料层褪色,而非颜料变化所致。建立了以具有较高热稳定性的赭石为颜料,以明胶作为粘接剂制成模拟的壁画颜料层。然后通过加热处理使胶料发生氧化分解,从而造成颜料层微观形貌发生变化,但赭石颜料依然稳定,期望证明在颜料赭石不发生变化时,由于颜料层微观形貌变化也可引起颜料褪色。实验通过煅烧壁画颜料层模拟样获得胶料降解的壁画模型,分别以SEM及多角度反射率光谱等技术,考察模拟样胶料降解前后表面微观形貌和光学性质变化。结果表明：壁画模拟样煅烧后,颜料层表面产生空隙结构,样品表面多角度反射率光谱表明煅烧后样品颜料层对可见光的反射增加而吸收降低,并观察到模拟样颜色淡化。以无色,难挥发,且不与颜料层发生化学反应的离子液体涂覆褪色样品表面,以上述技术表征涂覆处理前后颜料层表面微观形貌和表面光学性质变化,结果表明：离子液体填充了褪色样品表面颗粒间空隙,检测到样品表面对可见光的反射降低而吸收增加,观察到褪色样品的颜色加深。以上实验结果证明了推测合理性,即微观形貌变化确实会引起颜色变化。依据此原理以唐代墓室褪色壁画为例,进行了显现修复应用研究,其颜色显现效果显著。     

反刍动物源肉骨粉的近红外漫反射光谱判别分析

为了探讨利用近红外漫反射光谱判别分析技术快速鉴别非反刍动物源肉骨粉中是否掺有反刍动物源肉骨粉的可行性,收集了来源于国内不同地区的不同种类的肉骨粉样本39个,其中猪、鸡肉骨粉各15个,牛肉骨粉5个和羊肉骨粉4个。通过在非反刍动物源猪或鸡肉骨粉中人为掺入0%～48%的反刍类动物源牛或羊肉骨粉,制备了252个肉骨粉的样本。利用FOSS 6500型近红外光谱仪获取样本光谱,WINISI软件随机选取180个样本作为校正集,72个样本作为独立的验证集。采用基于偏最小二乘回归法(PLS)的判别分析技术,建立了判别分析模型,利用独立的验证集对判别分析模型进行了验证,最优判别分析模型正确判别率为90%。结果表明所建立的判别分析模型可以对非反刍动物源肉骨粉中含有的反刍动物成分进行快速鉴别,但对反刍动物成分含量低于2%的肉骨粉样本,模型的判别精度还有待提高。文章结果为反刍动物源性肉骨粉的鉴别分析提供了一种有效的快速筛选方法。     

The reflection and polarization properties of non-spherical aerosol particles

In this paper, we investigate the capability of multi-angle TOA reflectance and polarized reflectance for the retrieval of aerosol properties including aerosol mode (fine mode and coarse mode), aerosol shape (sphere and non-spherical), and aerosol optical thickness. Single-scattering parameters and phase-matrix elements were computed for randomly oriented non-spherical aerosol particles. Sensitivity indices were introduced to quantify the sensitivity of the TOA total reflectance and polarized reflectance to aerosol parameters. Finally, on the basis of the sensitivity study, this paper presents a conceptual approach toward the remote sensing of non-spherical aerosol three parameters (aerosol mode, aerosol shape, and aerosol optical thickness) using the TOA total reflectance and TOA polarized reflectance for the 0.865 μm spectral bands measured at multiple viewing angles.     

Chemically sprayed ZnO:(F,Zr) thin films: Effect of starting solution ageing time and substrate temperature on the physical properties

Conductive and transparent fluorine and zirconium co-doped zinc oxide [ZnO:(F, Zr)] thin films have been deposited onto sodocalcic glass substrates by the chemical spray technique. The effects of starting solution ageing time and the substrate temperature on the transport, structural, and morphological properties of as-deposited ZnO:(F, Zr) thin films are presented in this paper. A decrease in the electrical resistivity values is observed as the starting solution used is more aged, reaching a minimum resistivity of the order of 1.3×10^?2 Ω cm in samples deposited from a 17-day-aged solution, then increasing in samples deposited from solutions aged beyond this ageing time. According to the characterization results, the surface morphology is dependent on the solution ageing time. The X-ray diffraction patterns reveal that the ZnO:(F, Zr) thin films are polycrystalline in nature, fitting well with a hexagonal wurtzite structure, and showing the (0 0 2) planes as preferential growth in all the deposited films. The average optical transmittance, measured in the near UV–visible region, was of the order of 75% in all the cases.     

光学元件高反射比、高透射比测试技术研究

 为了实现光学元件、光学薄膜等高反射比、高透射比的测量,以单次反射测量法为基础,并结合激光稳功率技术、双光路测量技术以及精密探测技术,建立了一套精密测试系统,实现对光学元件632.8 nm和1 064 nm两个波长下高反射比与高透射比的测量。实验和测量不确定度分析验证测试系统在632.8 nm波长下高反射比与高透射比的测量不确定度优于0.008%,在1 064 nm波长下高反射比与高透射比的测量不确定度优于0.015%。     

掺Ga对ZnO电子态密度和光学性质的影响

采用密度泛函理论下的第一性原理平面波赝势方法,研究了掺Ga对纤锌矿ZnO电子态密度和光学性质的影响.从晶体配位场理论分析了掺Ga前后ZnO的成键情况及态密度的变化.计算得到掺Ga后电子浓度为2.42×10²¹ cm^-3,ZnO的载流子浓度提高了10⁴倍.比较分析掺Ga前后ZnO的介电函数、复折射率、吸收光谱和反射光谱可得,ZnO光吸收边向高能端移动,光学带隙增大.在可见光区,ZnO光吸收系数与反射率减小,光透过率显著提高,使ZnO:Ga成为 关键词： 密度泛函理论 态密度 光学性质 ZnO:Ga     

半色调双面图像的色彩预测Clapper-Yule模型

为了准确地预测印刷图像的光谱反射率,在假定油墨是非散射介质以及油墨的折射率与纸张的折射率近似相等的近似下,利用考虑光在纸基内多次内反射的Clapper-Yule理论和描述多重内反射的网状结构分析模型,建立了同色不同加网周期双面墨像的光谱反射色彩预测模型.同时给出了包含纸基的向下体反射和反面纸基-空气构成界面定向反射作用的单面墨像Clapper-Yule色彩预测修正新模型.     

基于多波段漫反射光谱古陶瓷窑口无损鉴定

古陶瓷是历史的遗存, 具有不可再生性，因而理想的古陶瓷分析技术应该是无损的。为客观、有效地对古陶瓷窑口进行无损鉴定，提出了一种基于紫外、可见光和近红外的多波段漫反射光谱无损鉴定方法。针对传统单一波段古陶瓷窑口鉴定对目标特征描述不足的问题，即在可见光波段区域，漫反射光谱数据可反映古陶瓷的颜色特征，但在同一窑口烧制的陶瓷也会有不同的颜色属性，仅仅根据可见光波段的漫反射反射率来鉴定窑口来源是不合理的，在紫外与近红外波段，古陶瓷内部分子与此波段光发生作用后的漫反射光谱数据，可反映古陶瓷携带的丰富样品结构和物质属性信息，结合紫外与近红外光谱漫反射光谱数据可有效提高特征的表达，因此提出利用紫外、可见光和近红外的多波段特征提取方法。在实验过程中，基于多波段线性特征融合窑口平均鉴定准确率为92.9%，相比于单波段的窑口鉴定平均准确率91.1%提高了1.8%，实验结果验证了所提多波段方法相对单波段方法的有效性；在特征提取过程中，常用小波变换对光谱信号进行处理，但由于古陶瓷漫反射光谱波信号在紫外、可见光与近红外波段形波动大，频率变化大，因此，在小波基的选取上存在很大困难，提出利用自适应时频分析特征提取方法，其特点是可自适应分配不同频率子波本征模态函数，通过选择合适的本征模态函数来提取古陶瓷不同波段的光谱特征，但在分解过程中存在过分解现象，即虚假的本征模态函数，将所有样本与分解的本征模态函数的平均相关系数和平均方差贡献率作为选择本征模态函数的标准，实验结果表明，随着分解阶次的递增平均相关系数和平均方差贡献率递减，当分解阶次为4时，相关系数和方差贡献率都为0.30，但当分解阶次为5时，相关系数和方差贡献率仅为0.15和0.18，因此选择4阶分解，用于不同波段的特征提取；所提取的特征给与分类器进行分类时，不同波段的特征对分类的准确率贡献不同，因此在此基础上，计算不同光谱特征的散布矩阵，利用类内与类间散布矩阵的迹，计算特征融合时不同波段特征的权重，自适应分配权重并进行非线性特征融合，权重越大，表明该类特征对鉴别的贡献越大，非线性特征融合时，平均鉴定准确率为94.5%，相比于线性特征融合鉴定平均准确率92.9%提高了1.6%；其中分类器采用k最近邻分类器对来自不同窑口的古陶瓷进行无损分类识别。通过客观定量地将该方法与同类方法进行对比，朱旭峰等利用非线性特征融合方法，窑口平均鉴定准确率为86.97%，该方法比其高7.53%。刘峰等采用基于协方差阵进行特征级融合多波段方法，窑口平均鉴定准确率为89.63%，该方法比其高4.87%。实验结果表明所提方法有效、可行，可作为古陶瓷窑口鉴定的有效辅助鉴定方法。     

Anisotropic optical properties of pure and doped polyacetylene

Optical absorption and reflection measurements have been carried out on pure and doped polyacetylene films. The absorption data are consistent with a model of (CH)_X as a direct gap quasi-l d semiconductor; doping with AsF₅ or iodine introduces absorption within the gap, but appears to leave the interband transition intact. The anisotropic reflectance from partially aligned films and the increased optical anisotropy upon doping provide evidence of quasi-l d behavior of the semiconducting pure polymer and the metallic doped polymer.