Parfenov, Vadim Aleksandrovich

Dobrusina S.A., Parfenov V.A., Podgornaya N.I., Samsygina N.D., Titov S.V., Petrov A.A., Aseev V.A.

Badillo P.D., Parfenov V.A., Raspopović R., Tishkin V.O.

Abstract 3D laser and optical scanning techniques are widely employed in Cultural Heritage preservation for documenting pieces of different sizes and shapes. However, due to limitations of the methods available today, the results obtained vary according to different characteristics of the object under study. External surfaces showing very smooth features make the capturing process and the posterior processing a more elaborate task, requiring special attention and additional retouching to improve the final 3D model. Tombstones are a typical example of this type of objects, combining both flat external contours and refined outlines. In this work the procedure of creation of the digital model of the tombstone of the bishop Vasilije Petrović (Negosh) is described, a piece of art which combines both technical and historical importance. Post-processing steps required involved different software (Geomagic Design X, ZBrush, Adobe Photoshop) for surface correction and cleaning, details and photorealistic texture improvements and lost material restoration.

Sharkova N.A., Vasilieva A.V., Parfenov V.A.

Vasilieva A.V., Kareva A.K., Parfenov V.A.

Jabr Y., Badillo P.D., Tishkin V., Parfenov V.A.

Badillo P.D., Parfenov V.A., Kuleshov D.S.

Salhab M., Rajasekara C.L., Vasiliev O.S., Karpov O.N., Parfenov V.A.

Ricci M., Sebastiani F., Becucci M., Rogozny M., Parfenov V.

We studied the painted decorations found during recent restoration work in the Alexander Palace in Tsarskoye Selo. Optical/laser spectroscopic methods were applied to obtain a characterization of the materials, pigments, and binders in use and, possibly, their degradation. We analyzed samples of the original Art Nouveau style decoration that was detached in 2019 during conservation work at the State Office of Emperor Nicholas II. A combination of Raman microscopy, infrared spectroscopy, and elemental analysis (obtained from the optical emission following laser plasma formation) allowed us to obtain detailed information on the materials used. The precious pigments of the artist’s green-blue palette and the binder used (drying oil) were identified. A mixture of blue (Prussian blue and ultramarine blue), white (lead white and barium white), and yellow (chrome yellow and zinc yellow) pigments determined the different blue hues used. The use of bronze paint in the dark blue area, which was identified as a brass powder applied with a drying oil as a binder, was also demonstrated.

Parfenov V.A., Igoshin S.D., Kuliashou D.

Vasilieva A., Kareva A., Zhankasheva G., Danilovich D., Parfenov V.

In this work, a painted gypsum bas-relief from the facades of the inner courtyard of the St. Petersburg Academy of Arts building was examined using UV and visible light photography and optical and electron scanning microscopy, which showed the heterogeneous layers of white painting on the surface of the bas-relief that covered the historical ones. These undesirable layers should be removed during the restoration work, but it was found that the traditional method of removing surface layers of painting with the help of chemical solvents and mechanical cleaning does not solve the problem to the full extent. A cross-section of all the painting layers was prepared to investigate the stratigraphy of the paint layers. These studies were conducted using optical and electron scanning microscopy in order to determine the structure of the paint layers more properly and study the chemical composition of every layer. After this study, a complex cleaning technique was developed. This technique combines chemical and laser cleaning, making it possible to effectively remove the upper dense layers of paint without damaging the historical paint layers.

Kravchenko P., Vasilieva A., Andrianov A., Parfenov V.

Ruzankina I., Mukhin N., Mermoul A., Parfenov V., Fron E., Ferrini G.

Single dielectric microspheres can manipulate light focusing and collection to enhance optical interaction with surfaces. To demonstrate this principle, we experimentally investigate the enhancement of the Raman signal collected by a single dielectric microsphere, with a radius much larger than the exciting laser spot size, residing on the sample surface. The absolute microsphere-assisted Raman signal from a single graphene layer measured in air is more than a factor of two higher than that obtained with a high numerical aperture objective. Results from Mie’s theory are used to benchmark numerical simulations and an analytical model to describe the isolated microsphere focusing properties. The analytical model and the numerical simulations justify the Raman signal enhancement measured in the microsphere-assisted Raman spectroscopy experiments.

Parfenov V., Galushkin A., Tkachenko T., Aseev V.

The purpose of this work is the study of laser cleaning of historical paper. The effect of laser exposure of the paper reflectance, fracture resistance and acidity was investigated. The paper surface roughness before and after laser treatment was analyzed by optical and scanning electron microscopy. It was shown that use of multi-pulse micromachining in combination with high-speed scanning of laser beams provides high safety for paper cleaning. The optimal parameters of laser radiation for effective and safe cleaning are a power density of about 2 × 105 W/cm2 at a wavelength of 1.06 μm, pulse repetition rate is 20 kHz; and a beam scanning speed of 200 mm/s–500 mm/s. The selective laser cleaning method for books and documents was proposed. Selective cleaning is achieved by means of high-precision control of the trajectory of movement of laser beams.

Badillo P.D., Jabr Y., Parfenov V.A.

Parfenov V., Igoshin S., Masaylo D., Orlov A., Kuliashou D.

Three-dimensional laser scanning is a novel measurement technique that is frequently used for the documentation of cultural heritage (CH) objects. In the process of 3D scanning, one can obtain computing 3D models of artworks to be documented. It allows one to produce detailed digitized archives of important CH objects. Moreover, the use of 3D scanning enables the digital reconstruction of architectural fragments, sculptures, and other artworks. One more important application of this technique relates to the creation of molds and replicas for replacements of outdoor CH objects in case their preservation requirements do not allow them to remain in their original place due to the influence of environmental factors. One of the most effective ways of creating replicas is the use of laser additive technologies. Therefore, the combination of 3D scanning and additive technologies is a very promising way of preservation of CH. This paper describes several case studies concerned with the combined usage of 3D laser scanning and additive technologies for digital reconstruction and replication and of outdoor sculptures in St. Petersburg city. One of them is the reconstruction of the zinc sculpture “Eva at the fountain” (XIX century, England), which was destroyed during WWII. Its replica was created by means of laser stereolithography. Eventually, one more project is related to the reconstruction of the fragment of the sufficiently damaged cast-iron XIX century monument. This object was reconstructed using two laser technologies: direct metal laser sintering (DMLS), and laser cladding (LC).

Wang Y., Bi W., Liu X., Wang Y.

Prakosa J.A., Alias N., Purwowibowo P., Algarni A.D., Soliman N.F.

Devoino O.G., Gorbunov V., Shpackevitch D.A., Lapkovsky A.S., Gorbunova V.A., Koval V.A., Kovaleva S.A.

A comparison of operating characteristics has been carried out for laser erosion cleaning (LC) processes studied in recent years and prospective for metalworking manufacturing of products/pieces from a number of carbon steels, cast iron and low-alloy non-ferrous metal alloys from oxidized layers formed as products of gas or other corrosion, often having inhomogeneous structure and porosity. To analyze the efficiency of various (in terms of layer composition) laser processes, it is advisable to use a group of parameters that affect the energy efficiency of LC-processing during the deoxidizing of surfaces. This group includes: a) the time-integrated energy criterion (Ken1s) of heating up to the melting point and/or evaporation temperatures of the layer and, sometimes, a metal substrate located underneath it (or the thermochemical efficiency of the heating, which is derived from the Ken1s), determined from energy consumption; b) irradiation power per surface unit (N0), or the ratio of N0 to the thermal conductivity of the layer; c) the pressure amplitude of the shock wave (SW) front in the laser plasma near the surface (Psw-p) or the dimensionless parameter that includes it, equal to the ratio of Psw-p to the shear stress for the oxidized layer/metal substrate interface. The dimensionless Ken1s criterion (or similar ones) will be more convenient in some cases for modeling and scaling of LC-processes than dimensional complexes, including thermal criteria such as DMF (“difficulty of melting factor”), which were tested in calculation of plasma spraying of ceramic materials. In this group of efficiency parameters, such a characteristic as the normalized (for example, with Ken1s) Peclet number, which characterizes the rate of propagation of the melting (or evaporation) boundary along the surface when scanning the beam, is also applicable. The considered characteristics, based on preliminary data, make it possible to evaluate the contribution of the mechanisms of the layer removal during pulsed LC, i.e.: 1) thermal effect (“ablation”) with “slow” heating to the melting point of the oxide (or to its evaporation temperature) in thermodynamically quasi-equilibrium regimes; 2) initiation of thermoelastic stresses in the crystal lattice of oxide phases under the impact of high power pulse, resulting in the formation of a network of cracks in the oxide film and its exfoliation from the metal substrate (“spallation”, it is approximately characterized by the maximum stress achieved during LC at the film/substrate interface); 3) plasmadynamic mechanism of the action of pressure on the surface due to the generation of near-surface plasma with a shock wave in it (with a pressure amplitude of up to ≥10 MPa). When assessing LC-processes taking into account efficiency characteristics, it is advisable to use a special set of verified data selected according to the thermophysical properties of layers of an analyzed type.

Bitelli G., Forte A., Tini M.A., Belfiori F., Tirincanti A.

In recent years, increasing attention has been directed toward the application of digitization through geomatic-based technologies for museum assets. These powerful tools have proven valuable in assisting museums in the dissemination of cultural heritage. Additionally, museums around the world are implementing strategies to improve the accessibility of their assets by involving the use of 3D digital reconstruction. The 3D high-precision survey is employed in several fields to scan objects with a geometrical accuracy up to the micrometer level. These technologies come into play when dealing with detailed surfaces and complex geometry, as often occurs with cultural heritage assets. This paper presents a set of experiences in high-precision 3D scanning and post-processing operations in the framework of a project at the Territory Museum of Riccione (Italy). The 3D data acquisition methodology conducted and digital operations are reported on for some of the scanned artifacts.

Li K.S.

Previous research has focused primarily on replicating bells that were expected to resemble the original closely in terms of material, size, shape, and tone. There has, however, been no effort to use original bells as templates from which to re-create or re-design new bells that deviate significantly in size, yet maintain the shape of the originals in order to address issues in the history of art and in the archeology of ancient China. Experimentation with ancient bells in this field remains largely untapped. This article proposes to re-create bells in enlarged and reduced sizes through casting, based on 3D-printed resin models that have been correspondingly scaled up and down, from a 3D model scanned from a 500 BCE bell that was excavated from Xinzheng in Henan province, China. The study seeks to answer a series of questions, including whether replication of bells was practiced in ancient times, how casters could predict the tones a bell would produce before casting, and how a set of bells used as a musical ensemble could have been developed over history.

Chamkouri H., Si J., Chen P., Niu C., Chen L.

Bartolini G., De Falco A., Gianfranceschi L., Martino M., Vignali L.

The structural diagnosis of monumental buildings necessitates organizing diverse cross-disciplinary data. The H-BIM procedure employs 3D digital models to create a comprehensive virtual repository, offering advantages in documentation access, interoperability, intervention design, cost evaluation, and maintenance management. This work proposes an approach to combining different models while addressing interoperability challenges by best exploiting their positive characteristics. After evaluating the advantages and limitations of textured-mesh and NURBS-based models, and virtual reality environments based on specific comparison criteria, an integrated system of these models within the H-BIM framework is proposed. The latter is applied to study the relevant case of the Baptistery of San Giovanni in Pisa, Italy. The integrated H-BIM model is designed primarily to facilitate the structural diagnosis of the monument, and illustrates how combining different 3D representations, each providing multiple information with different levels of detail, enhances its capabilities. This integration results in a more effective tool for the multidisciplinary conservation of cultural heritage, accommodating a wide range of data beyond structural aspects, thus fostering collaboration among professionals from various fields of expertise.

Neglia G., Angrisano M., Mecca I., Fabbrocino F.

Cultural heritage is, today, particularly exposed to the devastation resulting from natural phenomena, but it is even more exposed to the destruction caused by man-made ones. Consequently, it is critical to adopt suitable and concrete provisions for its preservation and conservation. The conflict that has been raging in Ukraine since February 2022 has spotlighted problems related to cultural heritage, which is increasingly considered a military target. Digital transformation and technologies integrated with legal tools can contribute to making the system of protection and recovery of cultural assets more effective and efficient by redefining methodologies to safeguard and interact with them. This paper proposes a framework for integrating legal and digital tools that are functional for the preservation, conservation, and enhancement of cultural heritage. To define it, on the one hand, the legal instruments in force were analysed, and on the other, a literature review on the digital technologies currently available was carried out. The role of digital transformation in the cultural sphere was also examined, especially in light of Ukraine’s experience with the application of digital technologies to protect and recover cultural heritage during the current conflict.

Prakosa J.A., Alias N., Purwowibowo P., Algarni A.D., Soliman N.F.

Dong Z., Liu X., Zhou S., Zhu Y., Chen J., Liu Y., Ren X., Lu Y., Xiao R., Wang G.

Surface enhanced Raman spectroscopy (SERS) utilizes the fingerprint features of molecular vibrations to identify and detect substances. However, in traditional single focus excitation scenarios, its signal collection efficiency of the objective is restricted. Furthermore, the uneven distribution of samples on the SERS substrate would result in poor signal stability, while the excitation power is limited to avoid sample damage. SERS detection system always requires precise adjustment of focal length and spot size, making it difficult for point-of-care testing applications. Here, we proposed a SERS microfluidic chip with barium titanate microspheres array (BTMA) embedded using vacuum self-assembled hot-pressing method for SERS detection with simultaneous enhancement of sensitivity and stability. Due to photonic nano-jets and directional antenna effects, high index microspheres are perfect micro-lens for effective light focusing and signal collecting. The BTMA can not only disperse excitation beam into an array of focal points covering the target uniformly with very low signal fluctuation, but enlarge the power threshold for higher signal intensity. We conducted a proof-of-principle experiment on chip for the detection of bacteria with immuno-magnetic tags and immuno-SERS tags. Together with magnetic and ultrasonic operations, the target bacteria in the flow were evenly congregated on the focal plane of BTMA. It demonstrated a limit of detection of 5 cells/mL, excellent signal reproducibility (error∼4.84%), and excellent position tolerance of 500 μm in X-Y plane (error∼5.375%). It can be seen that BTMA-SERS microfluidic chip can effectively solve the contradiction between sensitivity and stability in SERS detection.

Stech A., Kamencay P., Hudec R.

The increasing demand for accurate and detailed 3D modeling in fields such as cultural heritage preservation, industrial inspection, and scientific research necessitates advanced techniques to enhance model quality. This paper addresses this necessity by incorporating spectral imaging data to improve the surface detail and reflectivity of 3D models. The methodology integrates spectral imaging with traditional 3D modeling processes, offering a novel approach to capturing fine textures and subtle surface variations. The experimental results of this paper underscore the advantages of incorporating spectral imaging data in the creation of 3D models, particularly in terms of enhancing surface detail and reflectivity. The achieved experimental results demonstrate that 3D models generated with spectral imaging data exhibit significant improvements in surface detail and accuracy, particularly for objects with intricate surface patterns. These findings highlight the potential of spectral imaging in enhancing 3D model quality. This approach offers significant advancements in 3D modeling, contributing to more precise and reliable representations of complex surfaces.

Sergienko E.S., Tarakhovskaya E.R., Rodinkov O.V., Yanson S.Y., Pankin D.V., Kozlov V.S., Gareev K.G., Bugrov A.N., Kharitonskii P.V.

Ferromanganese formations are widespread in the Earth’s aquatic environment. Of all the mechanisms of their formation, the biogenic one is the most debatable. Here, we studied the Fe-Mn crusts of hydrothermal fields near the underwater volcano Puy de Folles (rift valley of the Mid-Atlantic Ridge). The chemical and mineralogical composition (optical and electron microscopy with EDX, X-ray powder diffraction, X-ray fluorescence analysis, Raman and FTIR spectroscopy, gas chromatography—mass spectrometry (GC-MS)) and the magnetic properties (static and resonance methods, including at cryogenic temperatures) of the samples of Fe-Mn crusts were investigated. In the IR absorption spectra, based on hydrogen bond stretching vibrations, it was concluded that there were compounds with aliphatic (alkane) groups as well as compounds with double bonds (possibly with a benzene ring). The GC-MS analysis showed the presence of alkanes, alkenes, hopanes, and steranes. Magnetically, the material is highly coercive; the blocking temperatures are 3 and 13 K. The main carriers of magnetism are ultrafine particles and X-ray amorphous matter. The analysis of experimental data allows us to conclude that the studied ferromanganese crusts, namely in their ferruginous phase, were formed as a result of induced biomineralization with the participation of iron-oxidizing and iron-reducing bacteria.

Bwanali M., Ugail H., Mnasri Z., Jensen E., Omar Z.

Bilušić M., Olivari L.

Optical 3D measuring systems serve as indispensable tools for the measurement and quality control of complex objects feeding process chains in industrial information integration. However, the accuracy of 3D measurements is influenced by a multitude of parameters, and the associated measurement uncertainties and influential factors remain insufficiently researched. This study investigates the effects of measurement object properties and software on measurement outcomes. Specifically, we examine seven geometries (diameter, distance, roundness, concentricity, flatness, parallelism and verticality) and four influencing factors (surface roughness, coating, polygonization, and interpolation). Our analysis employs variance analysis and compares the results with those obtained through linear regression using machine learning. In conclusion, the analysis of measurement uncertainty for optical 3D measurement systems in the assessment of seven distinct geometric characteristics provides a framework for determination of process chain suitability of the optical 3D measuring system.

Duliu O.G., Emandi A., Marinescu M., Cinteza O., Stanculescu I., Ionescu L., Filimon D.

To asses the degradation status of the Imperial Doors of the early 19th century Ascension Church iconostasis, a complex study consisting of micro-optical and scanning electron microscopy followed by energy-dispersive X-ray fluorescence and Fourier transform infrared spectroscopy was performed. Accordingly, the entire left door and some small fragments of gilded wood were investigated. The final results evidenced a certain degree of degradation of the lime wood and gilded surfaces, mainly due to the bacterial and fungi attacks given the increased humidity and the presence of more than a century of candle soot. Also, some unsuccessful restorations performed using brass paint instead of gold foils were evidenced. Overall, this study permitted elaborating more appropriate procedures for the iconostasis’ full restoration to its initial form, given that the Ascension Church is classified as a historical objective of national and universal value.

Ghervase L., Cortea I.M.

With the rapid scientific and technological changes that occur every day, a new kind of necessity, real-time, rapid, and accurate detection methods, preferably also non- or minimally invasive and non-destructive, has emerged. One such method is laser-induced fluorescence spectroscopy (LIF), applied in various fields of activity in recent decades, ranging from industry and biochemistry to medicine and even heritage sciences. Fluorescence-based spectroscopic methods have all of the above-mentioned characteristics, and their functionality has been proven in many studies. Yet, they have not known great success as other molecular techniques. This paper is a short synthesis of the role of the laser-induced fluorescence spectroscopy technique in heritage sciences, the main applications in this field, along with its advantages and limitations. The article focuses on the most common types of lasers used, the merging of two or more methods into hybrid techniques, the enhancement of the analytical capabilities of LIF and post-processing methods, and also explores some future development possibilities of LIF.

Parfenov V., Galushkin A., Tkachenko T., Aseev V.

The purpose of this work is the study of laser cleaning of historical paper. The effect of laser exposure of the paper reflectance, fracture resistance and acidity was investigated. The paper surface roughness before and after laser treatment was analyzed by optical and scanning electron microscopy. It was shown that use of multi-pulse micromachining in combination with high-speed scanning of laser beams provides high safety for paper cleaning. The optimal parameters of laser radiation for effective and safe cleaning are a power density of about 2 × 105 W/cm2 at a wavelength of 1.06 μm, pulse repetition rate is 20 kHz; and a beam scanning speed of 200 mm/s–500 mm/s. The selective laser cleaning method for books and documents was proposed. Selective cleaning is achieved by means of high-precision control of the trajectory of movement of laser beams.

Ogura T.

Circulating light in the total internal reflection within dielectric spheres or disks is called the whispering gallery mode (WGM), which by itself is highly sensitive to its surface and capable of detecting viruses and single atomic ions. The detection site of the sensors using WGM is created by the evanescent light from the circulating light inside spheres. Here we report anomalous Raman scattering enhancement in dielectric microspheres on a silicon nitride (SiN) film. This Raman enhancement occurs at the periphery of the spheres, and a similar ring of light was also observed under a fluorescence microscope. This is caused by the light circulating around the dielectric spheres as in the WGM. We observed anomalously enhanced Raman spectrum at the periphery of 3 μm diameter polystyrene (PS) microspheres on a SiN film using confocal laser Raman microscopy. The wavelength intensity of this enhanced Raman spectrum was accompanied by periodic changes due to interference. These features may lead to the development of high-sensitive sensors and optical devices.

Parfenov V., Igoshin S., Masaylo D., Orlov A., Kuliashou D.

Three-dimensional laser scanning is a novel measurement technique that is frequently used for the documentation of cultural heritage (CH) objects. In the process of 3D scanning, one can obtain computing 3D models of artworks to be documented. It allows one to produce detailed digitized archives of important CH objects. Moreover, the use of 3D scanning enables the digital reconstruction of architectural fragments, sculptures, and other artworks. One more important application of this technique relates to the creation of molds and replicas for replacements of outdoor CH objects in case their preservation requirements do not allow them to remain in their original place due to the influence of environmental factors. One of the most effective ways of creating replicas is the use of laser additive technologies. Therefore, the combination of 3D scanning and additive technologies is a very promising way of preservation of CH. This paper describes several case studies concerned with the combined usage of 3D laser scanning and additive technologies for digital reconstruction and replication and of outdoor sculptures in St. Petersburg city. One of them is the reconstruction of the zinc sculpture “Eva at the fountain” (XIX century, England), which was destroyed during WWII. Its replica was created by means of laser stereolithography. Eventually, one more project is related to the reconstruction of the fragment of the sufficiently damaged cast-iron XIX century monument. This object was reconstructed using two laser technologies: direct metal laser sintering (DMLS), and laser cladding (LC).

Yu B., Wang J., Miao S., Ren Y.

• Solubility of DH in three organic aqueous solutions at 303.15 to 348.15 K. • Experimental solubility data was correlated by four thermodynamic models. • Thermodynamic properties of mixing process were investigated. In this work, for further study on solubility behaviors of calcium sulfate dihydrate (DH) in different organic aqueous solutions, solubility of calcium sulfate dihydrate (DH) in three binary solvents (water + ethylene glycol, acetic acid, dimethyl sulfoxide) was experimentally investigated by the dissolution equilibrium method at (303.15 to 348.15) K under 88.35 kPa. Solubility data of DH first increased and then decreased with the temperature increased while reduced with the increasing molality of organic solvents. Experimental solubility data was correlated by four thermodynamic models including Wilson, modified Apelblat-Jouyban-Acree, UNIQUAC and NRTL model, all of them can well correlate the solubility of DH. Besides, thermodynamic properties of mixing process (Δ mix G , Δ mix S , Δ mix H , H 1 E,∞ and lnγ 1 ∞ ) were investigated based on solubility data and the Wilson equation.

Badillo P.D., Parfenov V.A.

Bertasa M., Korenberg C.

• Laser cleaning parameters must be tailored to each specific case study. • An overview of the literature and preliminary tests are essential to understand under which conditions laser cleaning is most likely to be successful on metals. • Laser wavelength and pulse duration are key parameters governing the removal of contaminants from metal artefacts. • When metals are covered with thick coatings or thick corrosion layers, better results can generally be obtained by combining laser cleaning with mechanical cleaning. • The laser cleaning of metals is often associated with side effects such as discolouration and micro-melting and the use of analytical techniques (e.g. scanning electron microscopy) is crucial to assess the laser cleaning outcomes. Over the past fifty years, laser cleaning has progressively become an established conservation cleaning treatment for a range of artefacts, including stone, ceramics and paintings. While its application to metal is not widespread, there have been several reports of laser cleaning on metal artefacts. However, the findings of these studies sometimes appear contradictory suggesting the laser cleaning outcome is strongly case-dependent and making it difficult to assess whether laser cleaning is a suitable technique for metal artefacts. The aim of this article is to give an overview of the research performed on the most commonly encountered metals in cultural heritage, i.e. copper, iron, silver and gold. This review shows that carefully selecting the laser wavelength, pulse duration and operating conditions (e.g. whether or not a wetting agent or inert gas is used) is crucial for optimising the laser cleaning outcome. It also highlights the importance of systematically assessing the outcomes of laser cleaning and will be helpful for conservators to understand whether laser cleaning might be suitable to conserve metal artefacts in their care. Further, this work represents a useful starting point for conservation scientists to plan future research in the laser cleaning of metals.

Son K., Lee W., Lee K.

This in vitro study aimed to evaluate the 3D analysis for complete arch, half arch, and tooth preparation region by using four analysis software programs. The CAD reference model (CRM; N = 1 per region) and CAD test models (CTMs; N = 20 per software) of complete arch, half arch, and tooth preparation were obtained by using scanners. For both CRM and CTMs, mesh data other than the same area were deleted. For 3D analysis, four analysis software programs (Geomagic control X, GOM Inspect, Cloudcompare, and Materialise 3-matic) were used in the alignment of CRM and CTMs as well as in the 3D comparison. Root mean square (RMS) was regarded as the result of the 3D comparison. One-way analysis of variance and Tukey honestly significant difference tests were performed for statistical comparison of four analysis software programs (α = 0.05). In half-arch and tooth preparation region, the four analysis software programs showed a significant difference in RMS values (p < 0.001), but in complete-arch region, no significant difference was found among the four software programs (p = 0.139). As the area of the virtual cast for 3D analysis becomes smaller, variable results are obtained depending on the software program used, and the difference in results among software programs are not considered in the 3D analysis for complete-arch region.

Pozo-Antonio J.S., Cardell C., Comite V., Fermo P.

Black crusts (BCs) are one of the most critical alteration forms found on stones belonging to architectural heritage. Since they could be considered as passive samplers of atmospheric pollution, it would be plausible to establish relations between the air contamination and the BCs. With this aim, we have characterized BCs collected on historic buildings from two Spanish cities (Granada and Vigo) with different polluted atmospheres, as well as formed on stone substrates of varied mineralogy and texture. Likewise, in order to assess the impact of the atmospheric pollutants on the growth of BCs, quartz fiber filters were used as surrogate substrates and placed nearby the studied buildings to collect and analyze the aerosol particulate matter (PM). To this end, an array of complementary analytical techniques was used to evaluate the mineralogy, chemical composition, and texture of the BCs and to establish the correlation with the ions, OC (organic carbon), and EC (elemental carbon) detected in the PM on the quartz fiber filters. As result, BCs developed on carbonate substrates from Granada show more complex structure than those from Vigo, which are thinner because of frequent rain episodes. In both cities, NaCl, Pb-Cl, and Ca-Cl-rich particles, Ca-phosphate particles and clusters of Ba-sulfate-rich particles were detected. However, metal-rich rounded particles were more abundant in Granada’s BCs, including soot particles. BCs from Granada were richer in carbonaceous components (OC and EC) than the Vigo’s BCs. Although in the filters PM did not show EC—mainly due to traffic—, in the BCs from both locations OC and EC were detected. Therefore, this different composition was related to the mineralogy of the stones and the higher pollution of Granada in contrast to the industrial and sea-exposed city of Vigo.

Lai H., Wang Y., Dai C., Hsueh C., Wang S., Li J.

Surface-enhanced Raman scattering (SERS) technique can increase the Raman signals of the analytes owing to the electric field enhancements on the nanostructures. The strong light intensity, called photonic nanojet, can be formed at the backlight of the dielectric microstructures. Recently, some researchers have applied the photonic nanojets in SERS. In this paper, a layer of synthesized low-cost polystyrene microspheres with the average of small particle size of 4.26 μm and high refractive index 1.5875 was prepared by dispersion polymerization method and coating on metal nanopillars SERS substrates using air-water interfacial floating method, and it was applied to improve the Raman signal sensitivity of kinetin (6-furfurylaminopurine) which is one kind of plant growth regulators and can function an effective compound for improving plant stress tolerance. The Raman intensity increased from 841 to 4449 for the Raman shift at 1327 cm -1 , about 5.29 times stronger. The SERS experiments using the kinetin of ultralow concentrations are measured and it shows that femto Molar can be measured. The numerical simulations indicated that the enhancement factor was about 4 times for plane wave illumination and 3.1 times for focused Gaussian beam. It has considerable potential for different analytes in sensing applications.

Ronchi A., Sterzi A., Gandolfi M., Belarouci A., Giannetti C., Fatti N.D., Banfi F., Ferrini G.

• Diagnostic tool for on-chip non-destructive testing of individual nano-objects. • Unsupervised clustering techniques applied to time-resolved thermo-acoustic optical microscopy. • Singular Value Decomposition (SVD) to reduce data space dimensions and approximate time-resolved traces. • Non destructive testing of single metallic nano-objects. • Asynchronous Optical Sampling (ASOPS) microscopy. Time-effective, unsupervised clustering techniques are exploited to discriminate nanometric metal disks patterned on a dielectric substrate. The discrimination relies on cluster analysis applied to time-resolved optical traces obtained from thermo-acoustic microscopy based on asynchronous optical sampling. The analysis aims to recognize similarities among nanopatterned disks and to cluster them accordingly. Each cluster is characterized by a fingerprint time-resolved trace, synthesizing the common features of the thermo-acoustics response of the composing elements. The protocol is robust and widely applicable, not relying on any specific knowledge of the physical mechanisms involved. The present route constitutes an alternative diagnostic tool for on-chip non-destructive testing of individual nano-objects.

Kashkool I.N., Afanasjev V.P., Mukhin N.V.

Abstract Electrical properties (carrier concentration, mobility, resistivity) of zinc oxide thin films deposited on glass substrates by (LPCVD) has been studied. Thermal annealing in air showed that ideal annealing temperature is about 250°C. Films of copper oxide (CuO) and (CuO/ZnO) solar cell were prepared by vacuum deposition of copper films followed by thermal annealing. structural properties of the CuO films and I-V characteristics were studied upon thermal annealing and showed that a photosensitive (ZnO/CuO) heterojunction may be obtained by thermal treatment temperature about 500°C.

Niklas C., Wackerbarth H., Ctistis G.

The market of gas sensors is mainly governed by electrochemical, semiconductor, and non-dispersive infrared absorption (NDIR)-based optical sensors. Despite offering a wide range of detectable gases, unknown gas mixtures can be challenging to these sensor types, as appropriate combinations of sensors need to be chosen beforehand, also reducing cross-talk between them. As an optical alternative, Raman spectroscopy can be used, as, in principle, no prior knowledge is needed, covering nearly all gas compounds. Yet, it has the disadvantage of a low quantum yield through a low scattering cross section for gases. There have been various efforts to circumvent this issue by enhancing the Raman yield through different methods. For gases, in particular, cavity-enhanced Raman spectroscopy shows promising results. Here, cavities can be used to enhance the laser beam power, allowing higher laser beam-analyte interaction lengths, while also providing the opportunity to utilize lower cost equipment. In this work, we review cavity-enhanced Raman spectroscopy, particularly the general research interest into this topic, common setups, and already achieved resolutions.

Darafsheh A.

Abstract Dielectric microelements with circular symmetry have shown interesting optical properties: photonic nanojets (PNJs) and whispering gallery modes (WGMs). They can confine light inside the cavity, forming WGMs, or focus the light in their proximity, forming PNJs. Both WGMs and PNJs have found numerous applications, including sensing and imaging. In this work, a review of PNJs and their applications in contemporary literature is provided.