Thermoluminescence Sensitivity Research Articles

Photonic crystal fibre as a potential medium for radiotherapy dosimetry

Present study concerns the key thermoluminescence (TL) properties of photonic crystal fibres (PCFs), seeking development of alternatively structured TL materials that are able to offer a advantages over existing passive dosimeters. In terms of their internal structure and light guiding properties the PCFs, collapsed and structured, differ significantly from that of conventional optical fibres. To investigate the dosimetric parameters of the PCFs use was made of a linear accelerator producing a 6 MV photon beam, delivering doses ranging from 0.5 Gy to 8 Gy. The parameters studied included TL response, linearity index, glow curves, relative sensitivity and TL signal fading, the results being compared against those obtained using TLD-100 chips. At 4 Gy photon dose the Ge-doped collapsed PCFs were found to provide a response 27 × that of structured PCF, also giving a TL yield similar to that of standard TLD-100 chips. Over post-irradiation periods of 15 and 30 days collapsed PCF TL signal fading were 8% and 17% respectively, with corresponding values of 37% and 64% for the structured PCF. Trapping parameters including the order of kinetics (b), activation energy (E) and frequency factor (s-1) were assessed with Chen's peak shape method. Lifetime of trapping centre was found to be (2.36 E+03) s and (9.03 E +01) s regarding the collapsed and structured PCF respectively with 6 Gy of photon beam. For the Ge-doped collapsed PCF, the high TL yield, sensitivity and low fading provide the basis of a highly promising system of TLD for radiotherapy applications.

Thermoluminescence in Eu doped NaLi2PO4TLD nanophosphor: Effect of particle size on TL characteristics

We report the thermoluminescence of Eu-doped NaLi2PO4 synthesized by solid state diffusion method. Formation of the material was confirmed by powder X-ray diffraction (PXRD) technique. Broadening of the PXRD peaks and field emission scanning microscope (FESEM) images were used for determining its particle size(s). Thermoluminescence (TL) characteristics were studied to see the effect of particle size after irradiating with γ -rays from 60Co source for wide-range (10 Gy-100 kGy) of doses. It was observed that not only TL sensitivity but also glow curve structure depends on particle size of the material. Glow curves were further deconvoluted using computerized glow curve deconvolution (CGCD) technique (after confirming the number of peaks using Tm-Tstop method) to study trapping parameters. TL glow curves mainly consist of four peaks appearing in the temperature ranges of 378–385, 426–435, 447–458 and 497–506 K. The shifts in the TL glow peak temperatures and the changes in glow curve structures can be attributed to the reorganization of local impurity levels (electron traps/luminescence centers) on widening of the band gap with reducing particle size. There can also be the effect of stress on glow curves developed due to crushing. Widening of the dose response with reducing particle size, easy method of synthesis, high sensitivity, low fading, good chemical stability, etc. make this TLD nanophosphor a good candidate for radiation dosimetry using TL.

Variation of luminescence sensitivity, characteristic dose and trap parameters of quartz from rocks and sediments

We investigated the optically stimulated luminescence (OSL) and thermoluminescence (TL) characteristics of quartz from sediments and parent rocks across South America. OSL and TL sensitivities were compared with the characteristic dose of dose response curves. Additionally, we estimated electron trap parameters of quartz from sediments with contrasting OSL sensitivities. Our results show that the natural sensitivities of quartz OSL (initial 0.8 s) and TL (110 °C peak) are positively correlated and range over six and four orders of magnitude respectively. The corresponding characteristic doses range from around 30 Gy–3000 Gy for dose response curves described by a single exponential function. Quartz from igneous and metamorphic rocks and Andean short-transported sediments report low-sensitivity OSL and high characteristic dose. The studied initial OSL signal has significant contribution of medium and slow components in quartz from rocks and Andean short-transported sediments, while in quartz from Brazilian long-transported sediments, the initial OSL signal is dominated by the fast component. The trend of sensitivity increase and characteristic dose decrease is attributed to the relative contribution of medium and low components to the initial OSL emission. Regarding the electron trap parameters, high, medium and low sensitivity quartz has statistically similar values of the activation energy and the frequency factor, but both parameters have larger variations in medium and low sensitivity quartz.

Impact of Zn2+ ions co-doping on the TL properties of Cu2+ ion-doped calcium lithium borate glass irradiated by various radiation sources

In this work, the effect of ZnO co-dopant on the thermoluminescence (TL) properties of Cu2O-doped calcium lithium borate glass was studied while the fabricated samples were irradiated with various radiation sources, namely gamma ray, 6 MeV electron and 6 MeV X-ray. Results showed that the addition of ZnO has led to the enhanced TL intensity and sensitivity by a factor of 4 and 3, respectively. This can be of special interest in incidental dosimetry; a linear response was obtained with all the beams. The thermal fading property was reduced by a factor 3, while the minimum detectable dose of the new dosimeter was 2.28 μGy. It was concluded that this dosimeter can be useful for personal, environmental, and medical radiation therapy applications.

Effect of using ultrasonic waves in synthesis on the size, shape and luminescence properties of NaCl:Ce3+ crystals for clinical dosimeter application

Cerium-doped sodium chloride micro and nanoparticles were synthesized without (sample a) and with (sample b) applying 20 kHz ultrasonic waves. Particles size and shape were identified by scanning electron microscopy and X-ray diffraction pattern. Using the Williamson Hall equation, the approximate sizes of ~462 nm and 45 nm were obtained for samples (a) and (b), respectively. Thermoluminescence glow curve as well as photoluminescence spectra of the both samples were also investigated. The results show that nanoparticles made in presence of ultrasonic waves have a smaller size and more homogeneous structure than those made in absence of ultrasonic waves. Photoluminescence emission of sample (a) and (b) correspondingly at 383 nm and 370 nm is related to the electron transfer from the 5d→4f bands. Furthermore, both samples are sensitive to gamma rays at high doses. The Thermoluminescence sensitivity of sample (a) is about six times more than that of sample (b) which confirms the dependence of Thermoluminescence sensitivity on the particle size. Fading of sample (b) within one month is about two times more than other of interest.

Facile synthesis and thermoluminescence properties of nano bio-ceramic \u03b2-Ca2P2O7:Dy phosphor irradiated with 75\xa0meV C6+ ion beam

Dy3+ doped β-Ca2P2O7 phosphor has been synthesized using wet chemical method. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis confirmed the formation of β-Ca2P2O7:Dy nano-phosphors. However, photoluminescence (PL) study was carried out to confirm the presence of dopant ion in the host matrix of β-Ca2P2O7:Dy material. Thermoluminescence (TL) glow curves of β-Ca2P2O7 were recorded for different concentrations of Dy3+ after exposure to various fluences of C6+ ion beam (75 meV). TL sensitivity of β-Ca2P2O7:Dy3+ (0.1 mol%) phosphor was 3.79 times more than commercially available CaSO4:Dy3+. TRIM code based on the Monte Carlo simulation was used to calculate the absorbed doses, ion range and main energy loss. Glow curve de-convolution (GCD) method was used to determine the number of TL peaks and their trapping parameters. The wide linear response of β-Ca2P2O7 nanoparticles along with high stability of TL glow curve makes this nanomaterial a good candidate for C6+ ion beam dosimetry.

Thermoluminescence in MgB4O7:Pr,Dy dosimetry powder synthesized by solution combustion synthesis method

This study aimed to investigate the dosimetric properties of magnesium tetraborate (MgB4O7) doped with praseodymium (Pr3+) and dysprosium (Dy3+) using the thermoluminescence (TL) technique. In this study, the dopant concentrations of Pr0.01–2% wt and Dy0.01–20% wt were induced into MgB4O7 with Solution Combustion Synthesis (SCS) method. Their effect was enhanced sensitivity of TL when used with the optimal dopant concentrations Pr0.5% wt and Dy5% wt incorporated in the lattice. The structural characterizations of MgB4O7:Pr0.5%wt,Dy5% wt phosphor was studied using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) analysis techniques. X-ray Luminescence (XL) spectra of several of these phosphors with various dopants as used here, were also determined. The TL glow curve of the MgB4O7:Pr0.5% wt, Dy 5% wt phosphor consists of four TL peaks at ~ 85, ~180, ~265, ~320 °C when recorded with a heating rate of 2 °C/s without preheating. Some dosimetric properties of the MgB4O7:Pr,Dy phosphor, such as dose-response, reusability and fading in dark were studied under 90Sr/90Y beta-ray radiation. The TL output was found as linear with dose from 0.1 to 100 Gy. The good reusability, by 2% standard deviation, was up to 20 experimental cycles. After 24 h, the maximum heights of TL glow peaks at 180 and 320 °C were about 7 and 4% less than that of the readouts at half an hour later the irradiation. The kinetic parameters using various heating rate (VHR), Tm-Tstop assisted extended initial rise method (IRM) and computerized glow curve deconvolution (CGCD) techniques were obtained and compared. Experimental results suggest that Pr3+ and Dy3+ doped MgB4O7:Pr0.5% wt,Dy5% wt shows suitable dosimetric properties for TL dosimetry.

Radiation dose from digital breast tomosynthesis screening – A comparison with full field digital mammography

ObjectivesTo compare Mean Glandular Dose (MGD) and effective dose from digital breast tomosynthesis (DBT) screening with that from full field digital mammography (FFDM) screening. MethodTo simulate compressed breasts, two Perspex-polyethylene breast phantoms were used, one phantom for compressed breast in craniocaudal and the other for compressed breast in mediolateral oblique. An adult ATOM dosimetry phantom was loaded with high sensitivity thermoluminescence dosimeters; the phantom was then positioned on Hologic Selenia Dimensions mammographic machine to imitate DBT and 4-view FFDM screening. Organ radiation doses were measured from 4-view DBT and 4-view FFDM (craniocaudal and mediolateral oblique views for each breast). Organ radiation doses were used to calculate effective dose from one screening session. ResultsMGD for DBT was 3.6 mGy; MGD for FFDM was 2.8 mGy. For DBT, other organs (e.g. thymus, lungs, salivary glands, thyroid, contralateral breast and bone marrow) radiation dose was also higher than for FFDM. The use of DBT for breast cancer screening increases the effective dose (E) of one screening session by 22%. E for DBT was 0.44 mSv; E for FFDM was 0.34 mSv. ConclusionThe use of DBT for breast cancer screening increases the radiation dose to screening clients.

Thermoluminescence and photoluminescence of magnesium-doped lithium tetraborate nanoparticles

Mg-doped Li2B4O7 nanophosphor was synthesized for the first time by using solid-state method, and the influence of magnesium dopant on the thermoluminescence dosimetry features was investigated. X-ray powder diffraction, scanning electron microscopy (SEM), photoluminescence (PL), Fourier transform infrared spectroscopy (FTIR) and UV–Vis spectroscopy analyses were utilized for identifying crystalline structure, morphology, particle size, borate groups and optical properties of the synthesized nanophosphor. Thermoluminescence sensitivity was enhanced by introducing magnesium dopant in LTB and reached a maximum at 0.5 mol% of impurity. The optimum pre-irradiation annealing regime was found at 400 °C for 15 min. Kinetic parameters and dosimetry characteristics, such as fading, dose response and reusability, are also presented and discussed.

Thermoluminescence based personnel neutron dosimetry study of LiMgBO3:Dy3+

The present paper reports the thermoluminescence (TL) based personnel neutron dosimetry studies of LiMgBO3: Dy3+ phosphor. It offers the great advantage of being a near tissue equivalent material with Zeff = 9.1. Also, the presence of both Li and B in the host matrix directly induce TL signal for neutrons. This is highly advantageous over CaSO4: Dy based TL neutron dosimeters where it requires to mix some thermal neutron sensitive species with the host matrix to induce neutron response. LiMgBO3: Dy3+ was synthesized by sol gel method and its structural characterizations were done by XRD, SEM and EDS techniques. TL upon irradiation with neutrons showed the glow peak at ~140 °C (413K). TL response up to 200 mSv of neutron dose showed very good linearity with adj. R2 = 0.998. 30% borated rubber discs were successfully utilised for the segregation of the gamma dose from the total dose in the mixed field (neutron + gamma) environments. The minimum detectable dose of the material was found to be 27.5 μGy and 2.7 μSv for gamma and thermal neutrons respectively. The TL sensitivity of LiMgBO3: Dy3+ for neutron and gamma radiation is 0.6 times and 0.3 times respectively with respect to that of standard TLD-100 [LiF: Mg, Ti] material. The proposed LiMgBO3:Dy3+ was also found to have better n/γ dose discrimination capability as compared to the commercially available TLD-100 material [LiF: Mg, Ti]. The kinetic parameters (viz. E, b and s) of the neutron irradiated TL glow peak were determined by Chen's peak shape and by variable heating rate methods.

A calcination study on BeO ceramics for radiation dosimetry

The aim of this study was to investigate the effect of calcination conditions on luminescence properties of BeO ceramics synthesized using co-precipitation and sol–gel methods. Structural and morphological characterizations were performed with X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) analyses. The role of calcination temperature and duration on micrograins' phase formation, morphology, grain-growth behavior, and luminescence characteristics were examined. Radioluminescence (RL), Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) techniques were used to characterize the luminescence signals. In the RL spectra of BeO ceramics synthesized with two methods, the characteristic emission peak between 200 and 500 nm, along with a wide emission peak between 700 and 800 nm due to anion defects were observed. To achieve a promising BeO dosimeter with highly sensitive TL and OSL signals for OSL dosimetry, the appropriate calcination conditions were determined for the co-precipitation and sol–gel methods as 900 and 1000 °C for 4 h, respectively.

Effect of size variation and gamma irradiation on thermoluminescence and photoluminescence characteristics of CaSO4:Eu micro- and nanophosphors

Microcrystalline CaSO4:Eu phosphor particles prepared by the acid re-crystallization method were grinded by ball-milling method and reduced to small particles of sizes ~50 nm, 200 nm, 400 nm and 5 μm. For comparison, nanocrystalline CaSO4:Eu phosphor of size ~20 nm was also prepared by chemical coprecipitation method. The recorded photoluminescence emission and excitation spectra revealed that Eu is doped in CaSO4:Eu in the form of Eu2+ and Eu3+ in all the samples of microcrystalline and nanocrystalline powders. The samples of CaSO4:Eu, with different particle sizes, were irradiated with gamma rays over a range of doses ranging from 1 Gy to 100 kGy. The results of characterization by thermoluminescence method show that the intensity of the thermoluminescence peak for a given dose of gamma-rays decreases with the decrease in the particle size of CaSO4:Eu. A comparison shows that CaSO4:Eu of size 50 nm exhibited linear response between the thermoluminescence peak and the gamma-ray dose in the range of 1 Gy–10 kGy. This phosphor can, therefore, be used for the measurement of gamma ray dose in medical and industrial applications. A comparative study also showed that the sensitivity of thermoluminescence to gamma ray dose for the nanophosphor prepared by the ball milling technique is better than that of the nanophosphor prepared by chemical co-precipitation method.

Calibration of MTS-N (LiF: Mg, Ti) chips using cesium-137 source at low doses for personnel dosimetry in diagnostic radiology

Thermoluminescent dosimeter (TLD) is still in use for many applications such as radiation protection, medical dosimetry, environmental research, and personnel dosimetry, with the overall aim of estimating radiation dose within a given medium or material. The aim of this study was to determine the coefficient of variation (CV) for thermoluminescent (TL) element within the same bar-coded slide and to establish calibration factors (CFs) at dose equivalent of 0.07 mm depth in tissue (Hp [0.07]) and dose equivalent of 10 mm depth in tissue (Hp [10]) for newly purchased TL elements alongside a new RadPro TLD manual reader and annealing oven. Annealed TL elements were taken to a Secondary Standard Dosimetry Laboratory (SSDL) for irradiation using a cesium-137 source at known doses (0.2–2 mGy). A RadPro Cube 400 manual TLD Reader was used to determine corresponding TL signal. The CV between two identical TL element within a bar-coded slide for (Hp [10]) and (Hp [0.07]) was determined and a graph of dose (mGy) against TL signal (Coulomb) was plotted to determine the elements CF. CVs from the raw data for 40 TL elements for Hp (10) and Hp (0.07) were 14.6% and 15.02%, respectively. Further selection of sensitive TL elements reduced the CVs of Hp (10) and Hp (0.07) to 3.73% and 3.21%, respectively, which was seen to be within ±10% accepted limit. The maximum percentage deviation for the calculated and actual dose for Hp (10) and Hp (0.07) was 16.7% and 14.3%, respectively. The CFs were power of 10 − 6 and the Coefficient of determination (R2) for Hp (10) and Hp (0.07) was 0.9998 and 0.9981, respectively, after adjustments were made on the initial graphs. Although large deviations were observed at low doses from the results of the raw data. Re-selected “golden Chips” had R2 close to unity and CV was within recommended standards.

The response of a dune succession from Lençóis Maranhenses, NE Brazil, to climate changes between MIS 3 and MIS 2

In tropical Southern Hemisphere South America, late Quaternary marine core and speleothem records provide different proxies and accurate chronologies correlating millennial-scale intervals of increased precipitation with southward shifts of the Intertropical Convergence Zone (ITCZ). However, the climatic effect of these intervals on coastal landforms is poorly understood. Here we investigated the response of abrupt and long-lasting climate events during the Marine Isotope Stages 3 and 2 in a 13.8-m thick sand succession located in a large-scale coastal eolian system, the Lençóis Maranhenses Dunefield, NE Brazil, where winds and precipitation are anti-phased and controlled by the single action of the ITCZ. A chronology of the sediment overburden determined by optically stimulated luminescence (OSL) dating of 14 sediment samples obtained at 1-m intervals showed ages between 132.2 ± 7.0 and 12.9 ± 0.6 thousand years ago in stratigraphic order. A multi-proxy approach based on grain size, surface grain texture, heavy minerals, thermoluminescence (TL) sensitivity, inorganic geochemistry, reflectance, and magnetic parameters from 268 sediment samples collected at 5-cm intervals indicated periods of dune building and stabilization. Significant stabilization periods are synchronous with Heinrich Stadials 6, 4, 3, 2, and 1, and Greenland Stadial 4, within age model uncertainties. Heavy mineral analysis indicated a steady sand source to the dune succession, while TL sensitivity analysis of quartz grains showed the input allochthonous sediments during stadials. The preservation of peak dune activity during the Last Glacial Maximum is attributed to the enduring precipitation brought by the subsequent Heinrich Stadial 1 event.

Dosimetric features and kinetic parameters of a glass system dosimeter.

Lithium borate (LB) glasses doped with dysprosium oxide (Dy2 O3 ) have been prepared by utilizing the conventional melt-quench technique. The prepared glass samples were exposed to 60 Co to check their dosimetric features and kinetic parameters. These features involve glow curves, annealing, fading, reproducibility, minimum detectable dose (MDD), and effective atomic number (Zeff ). Kinetic parameters including the frequency factors and activation energy were also determined using three methods (glow curve analysis, initial rise, and peak shape method) and were thoroughly interpreted. In addition, the incorporation of Dy impurities into LB enhanced the thermoluminescence sensitivity ~170 times. The glow from LB:Dy appeared as a single prominent peak at 190°C. The best annealing proceeding was obtained at 300°C for 30 min. Signal stability was reported for a period of 1 and 3 months with a reduction of 26% and 31%, respectively. The proposed glass samples showed promising dosimeter properties that can be recommended for personal radiation monitoring.

Effect of dopant concentration on luminescence properties of a phosphor KCaPO4: Dy

This paper reports for the first time the luminescence (both thermo and photoluminescence) properties of a new phosphor KCaPO4:Dy. The crystallite size of the phosphor prepared by solid-state diffusion method varied from approximately 46 nm–53 nm on varying the concentration of the dopant from 0.1 mol% to 0.4 mol%. Dopant concentration dependent bandgap mechanics in the phosphor was used to explain the behaviour of thermoluminescence (TL) glow curves obtained from gamma and ultraviolet irradiation, and photoluminescence (PL) spectra of the phosphor. Further, this phosphor shows good TL sensitivity towards gamma rays (2.5 times more sensitive than standard TL material TLD-100) and UV rays (20 times more intense than TLD-100). Moreover, the given phosphor shows good linear dose response for gamma rays (with linearity ranging from 10 Gy to 2 kGy) and UV irradiation. Deconvolution was also performed on the glow curves of the given phosphor for gamma irradiation (10 Gy) and UV irradiation (60 min) in order to calculate kinetic parameters for the traps. Other characteristics of the TL material i.e. repeatability and fading were also studied for this phosphor. Decent PL properties with an overall emission lying very near to the white region was observed through the chromaticity index of Commission Internationale de l’E’ clairage (CIE). All these characteristics make the phosphor (with 0.3 mol% Dy concentration) a potential candidate for radiation dosimeter and a UV convertible material for white-light-emitting diodes.

An investigation of luminescence properties of gamma, ultraviolet and ion-beam irradiated phosphor KCaBO3:Dy

Potassium calcium borate doped with dysprosium was synthesized by solid state diffusion method. Phase determination and compound confirmation were done by x-ray diffraction (XRD). Crystallite size calculated using Scherrer's formula was found to be around 117 nm. Other characteristics were studied using techniques like field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR). Band gap of the material was determined using ultraviolet–visible diffuse reflectance spectroscopy (UV-VIS DRS). The phosphor KCaBO3:Dy was irradiated by photon beams (of 1.25 MeV gamma and 4.88 eV UV rays) and ion beams (of 65 MeV and 85 MeV of O6+ and 75 MeV of C6+) with different doses in order to study its thermoluminescence (TL) properties. The phosphor showed good TL sensitivity towards these ionizing radiations. A good linear dose response was also shown by the phosphor for photon beam exposure. However, in case of ion beams exposure, dose response of the phosphor was good only for low energy oxygen ion beam. Also the phosphor showed good photoluminescence (PL) property with sharp peaks present in the PL emission and excitation spectra corresponding to the characteristic peaks of the dopant Dy. The Commission International de l’E clairage (CIE) was also used to calculate chromaticity coordinates and color temperature in order to investigate the phosphor's application in white LEDs. All these good characteristics make this phosphor a suitable candidate for radiation dosimetry and solid state lighting.

The TL-Properties of some Environmental Materials and Assessment the Effects of Other Different Parameters

In the present work, the Thermoluminescence (TL) properties of red sand sample collected from Nasr city, Cairo, Egypt was studied (the grain size effect, glow curve properties, dose response, batch homogeneity and fading). Surface morphology was studied using scanning electron microscopy (SEM). Chemical compositions of the red sand samples were estimated using X-ray fluorescence (XRF) machine. The analysis showed that the red sand sample mainly consisted of SiO2 (95.84%) and has feldspar which exhibits thermoluminescence. The experimental results illustrated that the optimum grain size ranges from 75 to150μm. After irradiation with γ-source (Co-60), the glow curves of the sample were found to have three peaks. The response curve has linearity in the dose range 10Gy – 2 kGy. Through 100 day, the total TL-signal fading reached 17%, but the dosimetric peak reached 12%. The measured activation energies of the peaks were deep enough to store the TL-signal. The pre-irradiation annealing at 800 °C for 1 h increased the TL sensitivity 2.295 times its original value. It could be concluded that the investigated samples could be used in environmental high γ-radiation measurements.

UVC dosimetry properties of Mn and Ce doped KCl thermoluminescent phosphor produced by co-precipitation method

Potassium chloride microcrystalline doped with Mn and Ce was successfully synthesized for the first time by the co-precipitation method and its thermoluminescence (TL) UVC dosimetry properties were investigated. The highest TL sensitivity was achieved at 0.3 and 0.5 mol% of Mn and Ce impurities respectively. The optimum annealing regime was found at 673 K for 15 min. The TL response is linear for illumination with UVC lamp up to 500 s. The optical band gap of 4.16 and 4.34 eV was obtained accordingly for the synthesized Mn and Ce doped KCl phosphor using the absorption spectrum. Tm-Tstop and computerized glow curve deconvolution procedures were used to identify the component TL glow peaks and kinetic parameters of the produced phosphor. Desired dosimetric features, besides the simple glow curve structure and separated glow peaks of the synthesized phosphors, presents them as good candidates for UVC dosimetry.

Thermoluminescent borates for environmental purposes

Ceramic samples based on lithium and divalent metal borates were obtained by solid-state reaction and their thermoluminescent response were tested. It is shown that calcium borate has the maximum thermoluminescent sensitivity. Co-doping of magnesium and calcium borates with monovalent metals result in an increase of the thermoluminescence intensity and appearance of a second thermoluminescence peak for calcium borate.