Optical Materials: X最新文献

{"title":"Modulation of spectroscopic properties in the YXO4 compounds (where X = V5+, P5+, As5+) doped with Eu3+ ions","authors":"Adam Watras ,&nbsp;Marta Kardach ,&nbsp;Katarzyna Szyszka ,&nbsp;Paulina Sobierajska ,&nbsp;Aleksandra Bartkowiak ,&nbsp;Rafal J. Wiglusz","doi":"10.1016/j.omx.2024.100377","DOIUrl":"10.1016/j.omx.2024.100377","url":null,"abstract":"<div><div>In the present work, a co-precipitation method was employed to prepare nanosized YXO₄ (X = V⁵⁺, P⁵⁺, As⁵⁺) doped with Eu³⁺ ions. The raw nanomaterials have been thermally treated in temperature range between 300 and 1100 °C for 3h. The XRD analysis demonstrated that the powders were single-phase with high crystallite dispersion. The studies focused on investigating the systematic relationship between crystallographic parameters and spectroscopic properties. The average size of the obtained materials was 30 nm for YVO4, 35 nm for YPO₄, and 20 nm for YAsO₄, respectively.</div><div>Moreover, the emission and excitation spectra, although typical for Eu³⁺ ions, demonstrated some degree of variability with calcination temperatures and doping concentration. Thermal luminescence quenching was typical for YPO₄ and YAsO₄ samples, while for the YVO₄ samples, the intensity of emission increased, reaching its maximum at 725 K. To explain this phenomenon, excitation spectra in function of temperature were measured.</div></div>","PeriodicalId":52192,"journal":{"name":"Optical Materials: X","volume":"24 ","pages":"Article 100377"},"PeriodicalIF":0.0,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effect of residual mechanical stresses and vacancy defects on the diffusion expansion of the damaged layer during irradiation of BeO ceramics","authors":"Azamat E. Ryskulov ,&nbsp;Igor A. Ivanov ,&nbsp;Artem L. Kozlovskiy ,&nbsp;Marina Konuhova","doi":"10.1016/j.omx.2024.100375","DOIUrl":"10.1016/j.omx.2024.100375","url":null,"abstract":"<div><div>The paper presents the results of a study on the application of Raman and UV spectroscopy methods to determine the structural damage kinetics in the near-surface layer of BeO ceramics caused by high-dose irradiation with He²⁺ ions. Interest in this type of ceramics is due to the combination of its structural and thermophysical parameters, making these ceramics one of the promising classes of materials for microelectronics and structural materials for nuclear reactors, with the possibility of operation in conditions of heightened radiation background. According to the conducted studies, it was established that with the irradiation fluence growth, changes in the nature of deformation structural distortions associated with the accumulation of residual mechanical stresses of tensile and compressive types are observed. At irradiation fluences of 10¹⁶–5 × 10¹⁶ Не²⁺/cm², tensile stresses play a dominant role in structural distortions, while the value of compressive stresses at fluence growth makes up a small share in the overall nature of the deformations. Moreover, an elevation in the irradiation fluence above 5 × 10¹⁶ He²⁺/cm² leads to a rise in the concentration of defects caused by the formation of oxygen vacancies, as well as He-V_O type complexes, the presence of which is indicated by the halo intensity growth in the Raman spectra, as well as a change in the intensity of the absorption bands. Analysis of changes in thermophysical parameters revealed that a rise in structural distortions associated with the accumulation of complex defects results in thermal conductivity reduction and a deterioration in heat transfer processes associated with partial amorphization of the damaged layer. Moreover, the established direct relationship between the value of residual mechanical stresses and the degradation of thermal conductivity indicates the cumulative effect of destructive changes caused by irradiation, as well as the influence of diffusion mechanisms on the damaged layer thickness growth.</div></div>","PeriodicalId":52192,"journal":{"name":"Optical Materials: X","volume":"24 ","pages":"Article 100375"},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of irradiation temperature on the mobility of structural and vacancy defects in the damaged layer of Li2ZrO3 ceramics","authors":"Bauyrzhan K. Abyshev ,&nbsp;Sholpan G. Giniyatova ,&nbsp;Artem L. Kozlovskiy","doi":"10.1016/j.omx.2024.100376","DOIUrl":"10.1016/j.omx.2024.100376","url":null,"abstract":"<div><div>The paper presents the assessment results of the irradiation temperature effect on the change in the type of structural defects caused by irradiation with helium ions in the near-surface layer of Li₂ZrO₃ ceramics, as well as determining the nature of structural damage using the electron paramagnetic resonance method in the case of irradiation fluence variation. During characterization of the structural changes caused by helium ion irradiation, the main attention was paid to detailing the type of structural defects and radiolysis products arising during irradiation, alongside alterations in their concentration using the electron paramagnetic resonance method. During the experiments, it was determined that the observed effects of thermally stimulated mobility of vacancy defects in the damaged layer caused by irradiation with helium ions indicate a positive effect of thermal heating of samples during irradiation at low fluences. This effect consists in a decline in the number of oxygen vacancies in the damaged layer at low irradiation fluences (10¹⁵–10¹⁶ cm⁻²), the concentration of which was determined using the EPR method, and the observed structural changes at low irradiation fluences in the case of an elevation in irradiation temperatures are associated with deformation distortion of the crystalline structure of ceramics caused by transformation energy processes, and thermal expansion effects.</div></div>","PeriodicalId":52192,"journal":{"name":"Optical Materials: X","volume":"24 ","pages":"Article 100376"},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Application of ion modification for alteration of anode materials based on ZnO/CoZn nanostructures","authors":"Ainur M. Zikirina ,&nbsp;Artem L. Kozlovskiy ,&nbsp;Inesh E. Kenzhina","doi":"10.1016/j.omx.2024.100374","DOIUrl":"10.1016/j.omx.2024.100374","url":null,"abstract":"<div><div>During the conducted studies, it was established that the use of ion modification by irradiation with O⁺ and Ar⁺ ions makes it possible to elevate the degradation resistance of anode materials due to the effect of vacancy defect creation, the density of which varies with the irradiation fluence. At the same time, the analysis of changes in the band gap and the optical density value, expressing changes in structural distortions, revealed that ion irradiation leads to a rise in the stability of the preservation of electronic properties during long-term resource tests, which are inextricably linked with the degradation of ZnO/CoZn nanostructures due to oxidation processes as a result of lithiation. During assessment of changes in the parameters of the band gap and optical density of the samples after resource tests, it was found that the observed growth in these indicators is due to oxidation processes and partial amorphization due to the formation of oxide inclusions in the structure of nanowires, the presence of which is due to the interaction of nanostructures with the electrolyte over a long period of time during charging/discharging, which results in near-surface layer degradation due to the introduction of oxygen, and in the case of a long service life, to the formation of oxide inclusions that elevate the density of defects and vacancies in the structure. According to tests of synthesized ZnO/CoZn nanostructures as anode materials, it was found that the use of O⁺ and Ar⁺ ions not only leads to a growth in the degradation resistance of capacitive characteristics during long-term tests, but also to the stability maintenance of indicators with a reversible decrease in the charging rate at charging rate variation.</div></div>","PeriodicalId":52192,"journal":{"name":"Optical Materials: X","volume":"24 ","pages":"Article 100374"},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Review of thermal neutron scintillators: Evaluation metrics and future prospects for demanding applications","authors":"G. Jeff Sykora,&nbsp;Sarah E. Mann,&nbsp;Giacomo Mauri,&nbsp;Erik M. Schooneveld,&nbsp;Nigel J. Rhodes","doi":"10.1016/j.omx.2024.100373","DOIUrl":"10.1016/j.omx.2024.100373","url":null,"abstract":"<div><div>Neutron applications are progressing rapidly, requiring detectors to meet increasingly rigorous criteria. Specifications such as high neutron counting rates, fast timing resolution and low background have a significant impact on choice of scintillator and how scintillators are evaluated. This work considers detector requirements for neutron scattering instruments that are becoming more stringent as the sources and scattering technologies continue to improve. Meanwhile, both prominent scintillators used for neutron scattering detectors, ZnS:Ag/⁶LiF and GS-glass, remain stagnant. While these scintillators have been suitable for many years, they are becoming a limiting factor for neutron scattering instruments. ZnS:Ag is inhibiting count rate capability and GS-glass is too gamma sensitive so alternatives need to be found. A brief explanation of neutron scattering, its detector requirements and how those relate to scintillator properties will be discussed. Furthermore, this work explains how standard characterization methods and reporting of scintillation properties are not entirely suitable for high count rate, low background applications like neutron scattering. As a result, modifications to characterization of gamma discrimination, light output, and decay kinetics are suggested. Additional steps are suggested including neutron activation and a more appropriate assessment of count rate capability. A non-exhaustive set of ⁶Li containing neutron sensitive scintillators including ZnS:Ag/⁶LiF, GS20 glass, ZnO:Zn/⁶LiF, Cs⁶LiYCl:Ce, ⁶LiI:Eu, ⁶LiI:Ce, ⁶LiCaAlF:Eu, LiCaAlF:Ce, transparent rubber sheet (TRUST) ⁶LiCaAlF:Eu, TRUST ⁶LiCaAlF:Eu with added fluorophore and EJ-270 (⁶Li containing plastic) are reviewed and studied from this different perspective. Finally, new scintillator developments relevant to high count rate, low background applications are discussed.</div></div>","PeriodicalId":52192,"journal":{"name":"Optical Materials: X","volume":"24 ","pages":"Article 100373"},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Scintillation properties of multilayered composite scintillators based on the YAG:Ce and TbAG:Ce single crystalline films and GAGG:Ce crystal substrates","authors":"Y. Syrotych ,&nbsp;V. Gorbenko ,&nbsp;S. Witkiewicz-Łukaszek ,&nbsp;T. Zorenko ,&nbsp;M. Kaczmarek ,&nbsp;J. Pejchal ,&nbsp;J.A. Mares ,&nbsp;R. Kucerkova ,&nbsp;M. Nikl ,&nbsp;K. Kamada ,&nbsp;A. Yoshikawa ,&nbsp;Yu Zorenko","doi":"10.1016/j.omx.2024.100372","DOIUrl":"10.1016/j.omx.2024.100372","url":null,"abstract":"<div><div>This work demonstrates current progress of our group in developing of two- and three-layered composite for radiation monitoring of various components of mixed ionization radiation fluxes based on the epitaxial structures of Ce³⁺ doped garnet compounds using the Liquid Phase Epitaxy growth technique. These scintillators contain one or two single crystalline films, dedicated for registration of low-penetrating particles, and bulk single crystal substrates used for detection of high-penetrating γ-rays. For creation of two- and three-layered epitaxial structures, the single crystalline films of Ce³⁺ doped Y₃Al₅O₁₂, Tb₃Al₅O₁₂ and Tb₂GdAl₅O₁₂ garnets were used. The single crystal of mixed Gd₃Ga_xAl_5-xO₁₂:Ce garnet with fixed Ga concentrations of x = 2.3 and 3.0 are utilized as substrates. To assess the scintillation properties of these epitaxial structures, the pulse height spectra, light yield and scintillation decay kinetics were measured under excitation by α–particles (²³⁹Pu), β-particles (⁹⁰Sr + ⁹⁰Y) and γ–rays (¹³⁷Cs). Finally, the figure-of merit of composite scintillators under study were calculated for selection of the best epitaxial structures for simultaneous registration α– and β-particles and γ–rays.</div></div>","PeriodicalId":52192,"journal":{"name":"Optical Materials: X","volume":"24 ","pages":"Article 100372"},"PeriodicalIF":0.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142432327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unusually high oxidation states of manganese in high optical basicity silicate glasses","authors":"Amir Ashjari ,&nbsp;Brian Topper ,&nbsp;Lars H. Hess ,&nbsp;Lucas Greiner ,&nbsp;Jared Tolliver ,&nbsp;Fiona Cormack ,&nbsp;Dimitrios Palles ,&nbsp;Efstratios I. Kamitsos ,&nbsp;Mikhail G. Brik ,&nbsp;Doris Möncke","doi":"10.1016/j.omx.2024.100371","DOIUrl":"10.1016/j.omx.2024.100371","url":null,"abstract":"<div><div>Unusually high oxidation states of manganese were stabilized within a cesium-barium silicate (CBS) glass system of extremely high optical basicity. The highest basicity was obtained for the metasilicate glass 40Cs₂O–10BaO–50SiO₂ (mol%) with an optical basicity of <span><math><mrow><mi>Λ</mi></mrow></math></span> = 0.81. The presence of Mn⁵⁺ (d²) as well as Mn⁶⁺ (d¹) is confirmed by UV–Vis, photoluminescence, and Raman spectroscopy. The UV–Vis spectrum is dominated by the Mn³⁺ (d⁴) absorption at 526 nm for low-basicity glasses, which is replaced by a peak at 679 nm (Mn⁵⁺) and, finally, a band at 603 nm (Mn⁶⁺) in the glass with the highest basicity (<span><math><mrow><mi>Λ</mi></mrow></math></span> = 0.81). In this glass, the Mn⁵⁺/Mn⁶⁺ ratio varies with the melting conditions. Photoluminescence (PL) spectroscopy under 633 nm excitation confirms the presence of Mn⁵⁺, showing the narrow, forbidden ¹E <span><math><mrow><mo>→</mo></mrow></math></span>³A₂ transition located at 1191 nm with vibrational sidebands at 1245 nm and 1290 nm. The measured static fluorescence intensity due to Mn⁵⁺ grows exponentially with increasing optical basicity. The near infrared fluorescence decay was bi-exponential, with time constants of 14 and 51 μs. The absence of Mn⁴⁺ in CBS glasses was confirmed by PL and electron paramagnetic resonance (EPR) spectroscopy. Despite initial doping as MnO₂, metastable Mn⁴⁺ disproportionates into lower and higher valent manganese species, followed by reduction or oxidation of manganese to a stable species as ruled by the basicity of the glass and oxygen availability during melting. A structural study of the glasses by Raman spectroscopy revealed a resonance enhancement effect for the symmetric stretching mode of MnO₄-tetrahedra at ∼800 cm⁻¹ with overtones observed at higher frequencies.</div></div>","PeriodicalId":52192,"journal":{"name":"Optical Materials: X","volume":"24 ","pages":"Article 100371"},"PeriodicalIF":0.0,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ZnYbAgO nanoparticles for the photocatalytic degradation","authors":"Trinh Duc Thien ,&nbsp;Nguyen Van Thang ,&nbsp;Le T.M. Cham ,&nbsp;Nguyen Dinh Lam","doi":"10.1016/j.omx.2024.100370","DOIUrl":"10.1016/j.omx.2024.100370","url":null,"abstract":"<div><div>The co-precipitation technique was used to produce Zn_1-x-yYb_xAg_yO nanomaterials. The Zn_1-x-yYb_xAg_yO nanomaterials have higher photocatalytic activity compared to ZnO, owing to their exceptional optical and electrical characteristics. The results demonstrate that the Zn_0.096Yb_0.02Ag_0.02O nanoparticles are capable of decomposing 98.2 % of RhB dye after 15 min by photodegradation. Moreover, studies have shown that superoxide radicals actively participate in the process of photodegradation.</div></div>","PeriodicalId":52192,"journal":{"name":"Optical Materials: X","volume":"24 ","pages":"Article 100370"},"PeriodicalIF":0.0,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419611","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of dicarboxystilbene impurities on the properties of swift heavy ion latent tracks in PET films","authors":"Adil Z. Tuleushev ,&nbsp;Fiona E. Harrison ,&nbsp;Artem L. Kozlovskiy ,&nbsp;Maxim V. Zdorovets","doi":"10.1016/j.omx.2024.100369","DOIUrl":"10.1016/j.omx.2024.100369","url":null,"abstract":"<div><div>We present a new hypothesis and supporting experimental evidence about the essential role played by small impurities of dicarboxystilbene in the process of UV treatment of PET films irradiated with swift heavy ions (SHI). This treatment both forms highly selective membranes with permeability values comparable to natural ones (the track-UV technique) and sharply accelerates the etching of latent tracks in membrane production (the track-etching technique). We hypothesize (1) that these high permeability value is due to the presence of a molecular motor of an Archimedes screw type in the central part of the latent track formed by photoinduced <em>trans-cis</em> isomerization of dicarboxystilbene molecules that are anchored in helical conformations in the latent track; and (2) that the acceleration of etching rates is due to the preferential accumulation of phenanthrene-type molecules in the central part of the latent track due to the existence of a cyclization channel for photoexcited molecules of <em>cis</em>-dicarboxystilbene. In the presence of alkali solution, phenanthrene molecules release electrons which behave as strong anions in aqueous solution, catalyzing alkaline hydrolysis of PET molecules in the central part of the track. We present experimental observations of photoinduced changes in transmission light intensity after track-UV light treatment of both pristine and SHI irradiated PET films that confirm the presence of <em>trans-cis</em> isomerization of dicarboxystilbene molecules and show their contribution to the formation of new helical conformations in SHI irradiated PET films during the light treatment.</div></div>","PeriodicalId":52192,"journal":{"name":"Optical Materials: X","volume":"24 ","pages":"Article 100369"},"PeriodicalIF":0.0,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study of the applicability of ACdSe (A – Co, Ni) thin films as catalysts for heavy metal capture","authors":"Aliya Zh Omarova ,&nbsp;Artem L. Kozlovskiy ,&nbsp;Gulnaz Zh Moldabayeva","doi":"10.1016/j.omx.2024.100366","DOIUrl":"10.1016/j.omx.2024.100366","url":null,"abstract":"<div><div>Expansion of the possibilities of using photoactive thin films with a unique combination of optical and morphological characteristics as a basis for creation of highly efficient catalysts for the aqueous media purification is one of the promising research areas in modern materials science, which has both fundamental significance and potential for practical application. This study examines the prospects for using modified thin CdSe films by substituting nickel or cobalt for cadmium and selenium as a basis for creating highly efficient catalysts for the aqueous media purification from heavy metals such as arsenic, manganese and iron. A rather inexpensive electrochemical synthesis method was proposed as a method for obtaining thin films, in which the substitution effect is achieved by addition of nickel or cobalt sulfates to the electrolyte, which allows obtaining films with an equally probable distribution of elements in the composition of the synthesized films. Optical spectroscopy methods were used as methods for characterization of the initial samples, which made it possible to establish the dependences of the change in the band gap and absorption bands on the composition of the synthesized films, as well as to anticipate the influence of morphological features on optical absorption. During the conducted studies it was established that partial substitution of nickel and cobalt for cadmium and selenium in the composition of films results in growth in the adsorption efficiency of heavy metals, alongside operation stability maintenance of modified films during cyclic tests. At the same time, enhancement of the adsorption efficiency of heavy metals for modified films is due to both an alteration in the optical properties of the films and morphological features associated with the specific surface area growth due to a reduction in the grain size and a more developed surface.</div></div>","PeriodicalId":52192,"journal":{"name":"Optical Materials: X","volume":"24 ","pages":"Article 100366"},"PeriodicalIF":0.0,"publicationDate":"2024-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142356639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}