Cleaning of artificially soiled paper with 532-nm nanosecond laser radiation

Cleaning of paper is a challenging task due to the fact that a contamination should be removed and a fragile organic original material has to be preserved. Pulsed laser cleaning of artificially soiled Whatman© filter paper samples serving as models for historical paper was performed. Different cleaning strategies employing 8-ns laser pulses at 532 nm wavelength were applied to clean paper avoiding undesired effects like discoloration (yellowing) and mechanical deterioration of the substrate. Multi shot experiments with low-energy pulses were compared with single pulse investigations utilizing high pulse energies achieving a constant energy load incident on the samples in both cases. The cleaning efficiency and possible yellowing effects were evaluated by means of a multi spectral imaging system. An extensive microscopic analysis of the cleaned parts of the samples provided insight into the remaining soiling on the surface and in the bulk of the paper material after laser treatment. As a reference, a hard and a soft eraser were used to clean the samples.     

Mechanistic comparison of pulse laser induced phase separation of particulates from cellulose paper at 213 nm and 532 nm

The laser-induced phase separation of charcoal particles on additive-free cotton linters cellulose paper was investigated by electron and optical microscopy, colorimetry, and diffuse reflectance FT-IR. The fibre bundles were vaporised in depth of several 10 μm above destruction fluence thresholds using visible 532 nm radiation. This is in contrast to mid-ultraviolet 213 nm radiation, where only the top fibre bundles were modified and partially evaporated. The colorimetric lightness results generally represented the cleaning status, whereas the colorimetric yellowing data represented irreversible chemical and/or photochemical changes. Charcoal-contaminated paper treated with visible and mid-ultraviolet radiation exhibited yellowing, whereas uncontaminated did not. This suggests that the electron-rich plasma generated by the evaporation of the particles heats the adjacent substrate and also excludes oxygen. Mid-ultraviolet, in contrast to visible radiation, shows particle removal always accompanied by paper destruction. IR spectroscopy results suggest cross-linking by ether bonds near the destruction threshold, but do not prove the formation of oxidation products and double bonds as the basis of the yellowing. A “cleaning window” between the cleaning threshold (0.1 J/cm²) and the paper destruction threshold (2.9 J/cm²) with a pulse number of 2 is provided by visible 532 nm laser treatment.     

ATR-FTIR and FT Raman spectroscopy and laser cleaning of old paper samples with foxings

Samples of old paper are studied using ATR-FTIR and FT Raman spectroscopy. It is demonstrated that the methods of laser spectroscopy make it possible to distinguish between the foxing localization regions and the region of homogeneous aging (yellowing). A significant bleaching of old paper and an almost complete erasure of the foxing stains can be reached using laser irradiation. Original Text ? Astro, Ltd., 2009.     

LED单色红光对西兰花采后黄化抑制效果的影响

光照是影响植物生长发育的重要因子,在植物生长过程中,对植物的生理代谢、光合特性、品质及衰老均有广泛的调节作用。然而国内外对于采后光照是否仍然可以提高果蔬品质,延长贮藏保鲜期的研究少见报道。采用红、蓝、绿三种单色光照射处理西兰花,红光对采后西兰花花球黄化具有抑制作用,蓝光抑制作用不明显,而绿光则加速了西兰花黄化,因此本文将重点研究LED单色红光对西兰花采后黄化抑制效果。采用波长为625±5 nm,光照强度(100±5)Lx的LED单色红光持续照射西兰花花球,以避光处理为对照。结果表明：LED单色红光能够抑制西兰花花球表面色差L值升高,保持色差-a/b值,延缓叶绿素降解;同时能够降低西兰花呼吸强度,推迟呼吸高峰,降低乙烯生成速率,有效保持了西兰花的商品性。相关性分析表明,采用LED单色红光处理后,乙烯生成速率与黄化指数之间达到极显著正相关水平(p<0.01)。与常规无光处理相比,LED单色红光处理延长了西兰花保鲜期5 d左右,为西兰花的贮藏保鲜提供理论依据。本文创新点在于首次将无化学污染、环境友好特性的LED单色光引入西兰花采后贮藏保鲜过程中,重点研究了LED单色红光对西兰花采后颜色变化的影响,明确了LED单色红光对西兰花采后黄化具有抑制作用。     

聚苯乙烯荧光乳液的制备及其性能研究

为了实现萘酰亚胺水性化以及提高与纸张的结合性,通过乳液聚合法制备了聚苯乙烯荧光乳液,并对其合成条件进行了优化。通过红外、凝胶渗透色谱法确定其结构;利用紫外、荧光光谱测定其光学性能;采用扫描电镜和透射电镜对其形貌进行了观测。通过计算得出其荧光量子产率为78.57%。聚合物涂布于纸张表面后,初始白度增大了8.19%（ISO）。在紫外老化箱老化48 h后,涂有聚合物的纸张的白度分别比空白纸和涂有小分子荧光增白剂的纸张下降了3.68%（ISO）和3.16%（ISO）,说明所制得的聚合物乳液与纸张结合性好,具有一定的增白及返黄抑制作用。     

IR pulsed laser light interaction with soiled cellulose and paper

Nd:YAG laser irradiation (1064 nm) of cellulose samples does not lead to immediate nor long-term effects on mechanical properties of paper, which renders the method increasingly interesting for cleaning of historical paper artefacts. However, the technique’s usability is so far limited due to discoloration when the treated object’s surface contains carbonaceous dirt. By using diffuse-reflectance Fourier-transform infrared spectroscopy, size-exclusion chromatography and viscometry it is demonstrated that the distinct yellowing is accompanied by formation of ether cross-links and dehydration of the cellulose, as well as its depolymerisation. Furthermore, the origin of the discoloration is discussed and it is proposed that yellow chromophores are formed due to carbon–cellulose interactions during laser irradiation. Received: 10 September 2001 / Accepted: 21 January 2002 / Published online: 3 June 2002     

Colour changes of a historical Gotland sandstone caused by laser surface cleaning in ambient air and N<Subscript>2</Subscript> flow

The surface discoloration due to laser cleaning was investigated for a historical Gotland sandstone. The difference in discoloration for cleaning performed in air and in the shielding environment of N₂ flowing at low velocities was studied by means of colorimetry and scanning electron microscopy and energy dispersive X-ray spectroscopy techniques. For ablative removal of the natural as well as artificially applied encrustation a pulsed 1064-nm laser operated at a fluence of 0.5 J/cm² was applied. It was observed that the natural colour variations (ΔL^*=21; Δb^*=23) of the stone can completely screen the laser-induced changes. Under conditions of shielding with nitrogen, darkening and yellowing slightly stronger than those occurring in the ambient air were revealed for the laser-cleaned, artificially crusted samples and the effect was independent of the gas-flow velocity. The observed difference confirmed the contribution of iron oxidation to the laser-induced yellowing and showed that the presence of oxygen in the ambient air affects favourably the cleaning by supporting removal of a variety of combustible surface remnants and crust components of organic as well as inorganic origin. PACS  42.62.-b; 52.70.Kz; 81.65.Cf     

Stochastic distribution of the fibrils that yielded the Shroud of Turin body image

The fibrils that yielded the Shroud body image show a stochastic distribution on the Linen of Turin. In fact, the probability of a fibril yellowing is a function of the energy, while this is not the case for the optical density value. This means that the above image is a latent image. We suggest thermal radiation or low-temperature chemical processes as possible natural energy sources to explain, by stochastic effects, the Shroud body image formation. Unfortunately, due to the nature of the phenomenon, we are not able to extract the energy source.     

The shape gradient of the least-squares objective functional in optimal shape design problems of radiative heat transfer

Optimal shape design problems of steady-state radiative heat transfer are considered. The optimal shape design problem (in the three-dimensional space) is formulated as an inverse one, i.e., in the form of an operator equation of the first kind with respect to a surface to be optimized. The operator equation is reduced to a minimization problem via a least-squares objective functional. The minimization problem has to be solved numerically. Gradient minimization methods need the gradient of a functional to be minimized. In this paper the shape gradient of the least-squares objective functional is derived with the help of the shape sensitivity analysis and adjoint problem method. In practice a surface to be optimized may be (or, most likely, is to be) given in a parametric form by a finite number of parameters. In this case the objective functional is, in fact, a function in a finite-dimensional space and the shape gradient becomes an ordinary gradient. The gradient of the objective functional, in the case that the surface to be optimized is given in a finite-parametric form, is derived from the shape gradient. A particular case, that a surface to be optimized is a “two-dimensional” polyhedral one, is considered. The technique, developed in the paper, is applied to a synthetic problem of designing a “two-dimensional” radiant enclosure.     

Ultrastructural insights into tomato infections caused by three different pathotypes of Pepino mosaic virus and immunolocalization of viral coat proteins

This paper presents studies on an ultrastructural analysis of plant tissue infected with different pathotypes of Pepino mosaic virus (PepMV) and the immunolocalization of viral coat proteins. Because the PepMV virus replicates with a high mutation rate and exhibits significant genetic diversity, therefore, isolates of PepMV display a wide range of symptoms on infected plants. In this work, tomato plants of the Beta Lux cultivar were inoculated mechanically with three pathotypes representing the Chilean 2 (CH2) genotype: mild (PepMV-P22), necrotic (PepMV-P19) and yellowing (PepMV-P5-IY). The presence of viral particles in all infected plants in the different compartments of various cell types (i.e. spongy and palisade mesophyll, sieve elements and xylem vessels) was revealed via ultrastructural analyses. For the first time, it was possible to demonstrate the presence of crystalline inclusions, composed of virus-like particles. In the later stage of PepMV infection (14 dpi) various pathotype-dependent changes in the structure of the individual organelles (i.e. mitochondria, chloroplasts) were found. The strongest immunogold labeling of the viral coat proteins was also observed in plants infected by necrotic isolates. A large number of viral coat proteins were marked in the plant conductive elements, both xylem and phloem.     

Effect of alkali metal on the properties of Bi-based glass powders prepared by spray pyrolysis

Bismuth-based glass powders with different quantities of Li₂O were directly prepared by high-temperature spray pyrolysis. The bismuth-based glass powders were completely spherical and submicron in size irrespective of the quantities of the Li₂O additive. The high optical transmittances of the dielectric layers formed from the glass powders obtained by spray pyrolysis were due to the decrease in the glass-transition temperatures of the glass powders with the addition of Li₂O. The ‘yellowing phenomenon’ was not observed in the dielectric layers formed from the glass powders obtained by spray pyrolysis, whereas it occurred in the dielectric layers formed from the glass powders obtained through the conventional melting process. PACS 42.70.Ce; 85.60.Pg; 71.55.Jv     

Quantification of oxygenated species on a diamond-like carbon (DLC) surface

This paper discusses the use of chemical derivatization methods for surface chemical composition analysis of diamond-like carbon (DLC) films synthesized through plasma-enhanced chemical vapor deposition with X-ray photoelectron spectroscopy (XPS). The main challenge in applying chemical derivatization reactions for titration of organic functional groups on the DLC surface is that sub-surface oxygenated species are not accessible to the derivatizing agent. As a simple approximation, a functional group that can be quantified unambiguously with XPS can be used as an internal reference to estimate the accessible-to-inaccessible ratio, and this information can be used to estimate the total amount of other functional groups from the chemical-derivatization-assisted XPS analysis. The use of this principle to obtain the surface composition of hydroxyl, ether, carbonyl, and carboxyl groups in the oxidized surface region of the DLC film was demonstrated.     

Application of extended thomas-fermi theory to the interlayer binding of graphite

Summary A functional for the calculation of the energy of a manyelectron system is applied to a simple model of a graphite crystal. The stationarity of the functional leads to an Euler equation which can be reduced analytically to an integral, which has been calculated numerically. The interlayer equilibrium distance and the compressiblity of graphite are found in good agreement with empirical values. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Free-matrix-based time-dependent discontinuous Lyapunov functional for synchronization of delayed neural networks with sampled-data control

This paper is concerned with the synchronization of delayed neural networks via sampled-data control. A new technique, namely, the free-matrix-based time-dependent discontinuous Lyapunov functional approach, is adopted in constructing the Lyapunov functional, which takes advantage of the sampling characteristic of sawtooth input delay. Based on this discontinuous Lyapunov functional, some less conservative synchronization criteria are established to ensure that the slave system is synchronous with the master system. The desired sampled-data controller can be obtained through the use of the linear matrix inequality(LMI) technique. Finally, two numerical examples are provided to demonstrate the effectiveness and the improvements of the proposed methods.     

Chaos game representation of functional protein sequences, and simulation and multifractal analysis of induced measures

Investigating the biological function of proteins is a key aspect of protein studies. Bioinformatic methods become important for studying the biological function of proteins. In this paper, we first give the chaos game representation (CGR) of randomly-linked functional protein sequences, then propose the use of the recurrent iterated function systems (RIFS) in fractal theory to simulate the measure based on their chaos game representations. This method helps to extract some features of functional protein sequences, and furthermore the biological functions of these proteins. Then multifractal analysis of the measures based on the CGRs of randomly-linked functional protein sequences are performed. We find that the CGRs have clear fractal patterns. The numerical results show that the RIFS can simulate the measure based on the CGR very well. The relative standard error and the estimated probability matrix in the RIFS do not depend on the order to link the functional protein sequences. The estimated probability matrices in the RIFS with different biological functions are evidently different. Hence the estimated probability matrices in the RIFS can be used to characterise the difference among linked functional protein sequences with different biological functions. From the values of the D_q curves, one sees that these functional protein sequences are not completely random. The D_q of all linked functional proteins studied are multifractal-like and sufficiently smooth for the C_q (analogous to specific heat) curves to be meaningful. Furthermore, the D_q curves of the measure \mu based on their CGRs for different orders to link the functional protein sequences are almost identical if q\geq 0. Finally, the C_q curves of all linked functional proteins resemble a classical phase transition at a critical point.     

Response function analysis of excited-state kinetic energy functional constructed by splitting k-space

Over the past decade, fundamentals of time-independent density functional theory for excited state have been established. However, construction of energy functionals for excited states remains a challenging problem. We have developed a method for obtaining these functionals by splitting k-space according to the occupation of orbitals. In this paper we demonstrate the accuracy of kinetic energy functional thus obtained for excited states with two sets of vacant orbitals. We then perform a response function analysis of the functional proposed and show why our method could be the method of choice for the construction of excited state energy functionals.     

Synchronization control of stochastic delayed neural networks

In this paper, synchronization control of stochastic neural networks with time-varying delays has been considered. A novel control method is given using the Lyapunov functional method and linear matrix inequality (LMI) approach. Several sufficient conditions have been derived to ensure the global asymptotical stability in mean square for the error system, and thus the drive system synchronize with the response system. Also, the estimation gains can be obtained. With these new and effective methods, synchronization can be achieved. Simulation results are given to verify the theoretical analysis in this paper.     

Prediction of adsorption of xenon in zeolite NaA with molecular density functional theory

The Tarazona model of molecular density functional theory is used to determine the adsorption isotherm and the density distribution of xenon atoms in zeolite NaA. We consider the alpha cage of NaA to be fully three-dimensional and we introduce a basis set for the density distribution to make the solution computationally tractable. The results of this density functional theory model are compared to previous results of grand canonical Monte Carlo simulations for the same system.We dedicate this paper to Professor Herbert Wagner, whose excellent contributions to density functional theory typify his valuable role in the advancement of statistical physics     

An Entropy Functional for Riemann-Cartan Space-Times

By viewing space-time as a continuum elastic medium and introducing an entropy functional for its elastic deformations, T. Padmanabhan has shown that general relativity emerges from varying the functional and that the latter suggests holography for gravity and yields the Bekenstein-Hawking entropy formula. In this paper we extend this idea to Riemann-Cartan space-times by constructing an entropy functional for the elastic deformations of space-times with torsion. We show that varying this generalized entropy functional permits to recover the full set of field equations of the Cartan-Sciama-Kibble theory. Our generalized functional shows that the contributions to the on-shell entropy of a bulk region in Riemann-Cartan space-times come from the boundary as well as the bulk and hence does not suggest that holography would also apply for gravity with spin in space-times with torsion. It is nevertheless shown that for the specific cases of Dirac fields and spin fluids the system does become holographic. The entropy of a black hole with spin is evaluated and found to be in agreement with Bekenstein-Hawking formula.     

A new approach to stability analysis of neural networks with time-varying delay via novel Lyapunov--Krasovskii functional

In this paper,new delay-dependent stability criteria for asymptotic stability of neural networks with time-varying delays are derived.The stability conditions are represented in terms of linear matrix inequalities(LMIs) by constructing new Lyapunov-Krasovskii functional.The proposed functional has an augmented quadratic form with states as well as the nonlinear function to consider the sector and the slope constraints.The less conservativeness of the proposed stability criteria can be guaranteed by using convex properties of the nonlinear function which satisfies the sector and slope bound.Numerical examples are presented to show the effectiveness of the proposed method.