Photo-, cathodo- and thermoluminescent properties of dysprosium-doped HfO2 films deposited by ultrasonic spray pyrolysis

In this work, the photoluminescent (PL), cathodoluminescent (CL) and thermoluminescent (TL) properties of hafnium oxide films doped with trivalent dysprosium ions are reported. The films were deposited on glass substrates at temperatures ranging from 300 to 600 °C, using chlorides as precursor reagents. The surface morphology of films showed a veins shaped microstructure at low deposition temperatures, while at higher temperatures the formation of spherical particles was observed on the surface. X-ray diffraction showed the presence of HfO₂ monoclinic phase in the films deposited at temperatures greater than 400 °C. The PL and CL spectra of the doped films showed the highest emission band centered at 575 nm corresponding to the transitions ⁴F_9/2→⁶H_13/2, which is a characteristic transition of Dy³⁺ ion. The greatest emission intensities were observed in samples doped with 1 atomic percent (at%) of DyCl₃ in the precursor solution. Regarding the TL behavior, the glow curve of HfO₂:Dy⁺³ films exhibited spectrum with one broad band centered at about 150 °C. The highest intensity TL response was observed on the films deposited at 500 °C.     

Synthesis,characteristics and thermoluminescent dosimetry features of γ-irradiated Ce doped CaF2 nanophosphor

Nanoparticles of cerium doped calcium fluoride (CaF₂:Ce) were synthesized for the first time using the hydrothermal method. The formation of nanostructures was confirmed by X-ray diffraction (XRD) patterns, indicating cubic lattice structure for the particles produced. Their shape and size were observed by scanning electron microscopy (SEM). Thermoluminescence characteristics were studied by having the samples irradiated by gamma rays of ⁶⁰Co source. The optimum thermal treatment of 400 °C for 30 min was found for the produced nanoparticles. The T_m−T_stop and computerized glow curve deconvolution (CGCD) methods, used to determine the number of component glow peaks and kinetic parameters, indicated seven overlapping glow peaks on the TL glow curve at approximately 394, 411, 425, 445, 556, 594 and 632 K. A linear dose response of up to 2000 Gy, was observed for the prepared nanoparticles. Maximum TL sensitivity was found at 0.4 mol% of Ce impurity. Other TL dosimetry features, including reusability and fading, were also presented and discussed.     

LiSr4(BO3)3:Ce3+ phosphor as a new material for ESR dosimetry

LiSr₄(BO₃)₃:0.01Ce³⁺ phosphor was investigated to assess its potential as a material for measurements of radiotherapeutic doses with electron spin resonance (ESR). The ESR spectrum of the phosphor irradiated with ⁶⁰Co features five ESR signals. An isochronal annealing experiment has shown that the strongest of these signals is associated with the same trap center as the 473 K peak on the TL glow curve of this material. The dose–response is linear in the studied range from 0.89 to 90.30 Gy. Fading of the signal was also investigated.     

Thermoluminescent response of single crystal Al2O3:Fe

Thermoluminescence characteristics of iron doped aluminum oxide (Al₂O₃:Fe) single crystals were studied. The glow curve of x- and γ-ray irradiated Al₂O₃:Fe single crystals while being heated up to 375°C consisted essentially of an intense isolated single peak at 193°C and small peaks at 250° and 285°C. But the study was carried out on 193°C peak because of the accuracy of measurements and the possibility of using it a thermoluminescence dosimeter. The trap depth and escape frequency factor were calculated to be 1.156 eV and 3.1 × 10¹¹ s⁻¹ respectively. Dose-response was investigated between dose ranges of 5 × 10² mR and 10⁴R for ¹³⁷Cs γ-rays. Dose-response was found to be linear in this range. The energy dependence was 5% between 33 and 662 keV when the thermoluminescent responses were normalized to ¹³⁷Cs γ-rays. It is suggested that Al₂O₃:Fe may be used as a γ radiation dosimeter in high dose environments such as oncology hospitals, radiobiological centers, nuclear reactors.     

Thermoluminescent response of CaSO4:Dy+PTFE induced by X-ray beams

The aim of the present work was to evaluate the feasibility of the utilization of CaSO4:Dy pellets for X-ray measurements in a general radiology department. Thermoluminescence (TL) response of CaSO4:Dy+PTFE was compared to the TL response of commercial LiF:Mg,Ti (TLD-100) samples. TL pellets were exposed to X-ray beam from X-ray machine CMR for clinical diagnosis purpose. The calibration curve of CaSO4:Dy+PTFE was obtained and it showed a linear response as a function of absorbed dose in air at the studied dose interval. Despite this fact, this material can be used for X-ray beams measurements if appropriate calibration procedures are performed.     

Thermoluminescence studies of LiSrBO3:RE3+ (RE=Dy,Tb, Tm and Ce)

The polycrystalline samples of LiSrBO₃:RE³⁺ were synthesized by high-temperature solid-state reaction. The influence of different rare earth dopants, i.e. Dy³⁺, Tb³⁺, Tm³⁺ and Ce³⁺, on thermoluminescence (TL) of LiSrBO₃ phosphor was discussed. We also investigated some dosimetric characteristics of LiSrBO₃:Tm³⁺. The effect of the concentration of Tm³⁺ on the TL intensity was investigated and the result of which showed that the optimum mole fraction of Tm³⁺ was 1%. The TL kinetic parameters of LiSrBO₃:0.01Tm³⁺ were calculated by the computer glow curve deconvolution (CGCD) method. We also studied the three-dimensional (3D) TL emission spectrum of LiSrBO₃:0.01Tm³⁺ under gamma-ray irradiation. The dose-response of LiSrBO₃:0.01Tm³⁺ to γ-ray was linear in the range from 1 to 400 m Gy.     

Magnetic field dependence of solvent proton relaxation induced by Gd3+ and Mn2+ complexes

The effect of solute paramagnetic ions on the longitudinal magnetic relaxation rate 1/T¹ of solvent water protons depends on magnetic field strength and on the chemical environment of the ions. The variation of 1/T¹ with field has been measured for solutions of Gd³⁺ and Mn²⁺ ions in three grossly different environments near physiological pH: the hydrated aquoion; chelated by EDTA (ethylenediaminetetraacetic acid) and DTPA (diethylenetriaminepentaacetic acid); and bound to the protein concanavalin A. It is demonstrated that over the field range at which NMR imaging is currently being done, the chemical environment can alter 1/T¹ of solvent protons by more than an order of magnitude. The relevance of these results to the potential utility of these ions as agents for enhancement of contrast in NMR images is discussed.     

Magnetic field dependence of solvent proton relaxation rates induced by Gd3+ and Mn2+ complexes of various polyaza macrocyclic ligands: implications for NMR imaging

The magnetic field dependence of the solvent water proton longitudinal relaxation rate 1/T1 (the NMRD profile) has been measured for solutions of chelates of Gd3+ and Mn2+ ions with two different polyaza macrocyclic ligands: 1,4,7-triazacyclononane-N,N',N",-triacetic acid (NOTA) and 1,4,7,10-tetraazacyclododecane-N,N',N",N'"-tetraacetic acid (DOTA). Studies were carried out mainly near physiological pH, but the pH dependence was also examined in some cases. The results are compared with published data for complexes of Gd3+ and Mn2+ ions with ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA). Competition experiments for the NOTA and DOTA chelates with EDTA and DTPA were also performed. It is found that, over the field range in which NMR imaging is currently being done, different symmetries of otherwise similar chemical ligands can alter 1/T1 of solvent protons by factors of up to three. The ligand environment can influence the relaxation times of the electronic spin moments of the ions, as well as their coordination number, thereby changing both the inner and outer sphere contributions to the relaxivities of the complexes. The relevance of these results to questions of efficiency and toxicity of these chelates as agents for enhancement of contrast in NMR images is discussed.     

Detection and characterization of very small cerebral aneurysms by using 2D and 3D helical CT angiography

BACKGROUND AND PURPOSE: Many cases of subarachnoid hemorrhage are due to rupture of small cerebral aneurysms. Our purpose was to evaluate the usefulness of helical CT angiography (CTA) in the detection and characterization of very small (<5 mm) intracranial aneurysms. METHODS: One hundred eighty consecutive patients underwent CTA for suspected intracranial aneurysms. All aneurysms prospectively detected by CTA were confirmed by digital subtraction angiography (DSA) or at surgery. CT angiograms and digital subtraction angiograms were reviewed by two independent blinded radiologists who performed aneurysm detection, quantitation, and characterization using 2D multiplanar reformatted and 3D volume-rendering techniques. RESULTS: Fifty-one patients harboring 41 very small intracranial aneurysms were included in this series. Eighty-one percent (33 of 41 aneurysms) were 相似文献   

Sources of carbon which decrease the specific activity of [11C]CH3I synthesized by the single pass I2 method.

The sources of carbon, which decrease the specific activity of [11C]Methyl iodide [11C]CH3I synthesized by the single pass I2 method were, determined. Some organic solvents (acetone, CH3OH and THF etc.) and non-volatile oils (silicone oil and paraffin) could react with the I2 vapor to yield the non-radioactive CH3I in the heated quartz tube, which decreased the specific activity of [11C]CH3I significantly.     

Structure-function analysis of Squaraines phototherapeutic activity: in vitro characterization of ROS and intracellular Ca2+ signals interplay in phototoxicity

Photodynamic therapy (PDT) is an emerging, minimally invasive therapeutic modality approved by the U.S Food and Drug Administration for the treatment of several conditions including oncological applications ¹. The approach is based on light-induced photosensitizers (PS) activation which, in turn, promotes the intersystem crossing and triplet state that easily reacts with molecular oxygen, thus generating free radicals and singlet oxygen species which in turn involve intracellular Ca2+ signals as well as other messengers with a final increase in apoptosis, necrosis, and autophagy processes and tumor mass reduction ^1,2. In this context, the development of new PS for the PTD is of great interest to increase the treatment efficacy minimizing side effects^3,4.In the present work, we investigated the structure-functional role of SQ by comparing the phototoxic activity of unsubstituted SQ, carboxyl (COOH)- and bromine (Br)-substituted SQ, as well SQ in which the oxygen atoms of the squaryl ring were replaced with sulfur atoms (S-SQ). Indeed, the presence of heavy atoms such as Br and the replacement of oxygen with sulfur are predicted to shift the emission to the far NIR region and increase the quantum yield of singlet oxygen, thus improving the overall effect in PDT. As expected, Br-SQ and S-SQ demonstrate a higher phototoxicity on MCF-7 cells compared to the COOH-SQ dye, which showed no effect. However, surprisingly, our data reveal that also the unsubstituted SQ has a strong phototoxic activity. To deeper analyze the the molecular mechanisms underlying SQ phototoxicity, we studied the role of Ca2+ signals and ROS generation in light induced PS activation. Our results clearly show that Br-SQ promote ROS production as well as significant increase in cytosolic Ca2+ signals mainly due to Ca2+ release form ER stores which in turn promotes a sustained Ca2+ uptake in the mitochondria while no effect was observed for the COOH-SQ. Our results shed new light on the structure-function relationship of SQ and the intracellular pathways involved in their exploitable photo-activity in PDT, demonstrating a critical role for intracellular Ca²⁺ signals in ROS activation and cell death.     

以“3＋2＋1”模式实现优质医疗资源下沉， 让老百姓在“家门口”享受三甲医院医疗服务

【摘要】与成都市郫都区人民医院建立紧密型医共体的成都市郫都区人民医院安德分院新院区在2020年7月1日全面开诊,这意味着在区域医共体新模式下,将三甲医院优质医疗资源直接送到了老百姓“家门口”,是一份实实在在的民生大礼。成都市郫都区人民医院安德分院充分利用区域医共体这个平台,以“三个相通”“两个帮扶”“一个联动”模式实现了与成都市郫都区人民医院的紧密结合,提高了区域医疗资源使用效率,实现了优质医疗资源下沉,切实解决了基层老百姓看病难、看病贵、看病不方便等问题。     

Specific activity of [11C]CH3I synthesized by the “wet” method: Main sources of non-radioactive carbon

Positron emission tomography (PET) is a powerful molecular imaging technique based on the administration and detection of radioactive (positron emitting) species. In some applications, the concept of specific activity becomes especially important in order to prevent undesired pharmacological and/or toxic effects after injection of the radiotracer. Problems to obtain high specific activities are found when ¹¹C-labeled compounds are prepared by methylation following the so called “wet” method, which consists of a simple route but usually yields radiotracers highly diluted with the stable specie. In the present work, the main sources of contamination by stable carbon in the [¹¹C]CH₃I synthesis following the “wet” method have been analyzed and their individual contribution has been quantified. The results show that the most relevant contamination of CO₂ is generated during the bombardment process.     

Thin CaSO4:Dy thermoluminescent dosimeters for calibration of Sr+Y applicators

Clinical applicators are used in brachytherapy to treat superficial lesions of skin and eye. They should be periodically calibrated according to quality control programs and international recommendations. Thin CaSO₄:Dy thermoluminescent dosimeters were used to calibrate various applicators with a dermatological applicator as a reference. The obtained absorbed dose rates were compared with those quoted in their calibration certificates. Depth-dose curves were constructed for all the applicators. A mail dosimetry system was developed for calibration of clinical applicators.     

Relaxation of solvent protons by solute Gd3+-chelates,revisited

The magnetic field dependence (NMRD profile) of 1/T₁, of solvent protons in an aqueous solution of Gd(DTPA)^2? was remeasured at 5,15,25,30, and 35°C. The data were reanalyzed with the usual low-field theory, using recently published values for T_M, the residence lifetime of the single inner-coordinated waters of solute Gd(DTPA)^2?. (These T_M values are significantly longer than earlier estimates). Values were obtained for three dynamic parameters: T_R, the rotational relaxation time of solute ions, and T_SO and T_V, the low-field relaxation time of the Gd³⁺ magnetic moment and the related correlation time. These Gd(DTPA)²⁺ values, together with recent results for T_M for Gd(DTPA-BMA) — a nonionic structural analog of Gd(DTPA)^2? with an unusually long T_M — were used to calculate NMRD profiles at 5 and 35°C. These profiles agree very well with new data given here for a solution of Gd(DTPA-BMA). This reaffirms the importance of knowing the temperaturedependent values of T_M a priori in order to obtain unambiguous quantitative theoretical analyses of NMRD profiles of chelates of known structure. Additionally, the theory of inner sphere relaxation is extended to high fields, at which the magnetic energy of a solute moment is greater than its thermal energy.     

The on-line characterization of a radium slurry by γ-ray spectrometry

We have developed an in-line monitor to directly measure the ²²⁶Ra concentration in a nuclear waste stream using quantitative gamma-ray spectrometry applied to the 186 keV emission. The waste stream is in the form of a slurry composed of the solid waste material mixed with water. The concentration measurement includes a self-attenuation correction factor determined from a transmission measurement using the 122 keV γ from ⁵⁷Co. Presented here is the model for the measurement system and results from some initial tests.     

Enhancement of Radiation-induced Sterility in Insects by Pretreatment in CO2 + Air

Summary

When the pupae of the screw-worm fly (Cochliomyia hominivorax (Coquerel)) are irradiated in an atmosphere of CO₂ + air (50–50 mixture), damage to the reproductive system measured in the adult female is greater than that induced by a similar radiation treatment delivered in air. Doses of gamma-radiation ranging from 2500 to 5000 r were investigated. In all tests the number of females ovipositing, the number of eggs per fecund female, and the egg hatchability were reduced. For CO₂ to be effective in enhancing radiation damage air must be present, and the pupae must be pretreated in the gas mixture for approximately 45 minutes. Complete sterility can be induced by a treatment of 4500 r delivered in CO₂ + air, whereas irradiation in air alone requires about 5500 to 6200 r to induce complete sterility. Irradiation in CO₂ + air is more damaging to the reproductive system than irradiation in pure oxygen.     

Biosorptive behaviour of Mango (Mangifera indica) and Neem (Azadirachta indica) bark for Hg2+, Cr3+ and Cd2+ toxic ions from aqueous solutions: a radiotracer study

Biosorption of Hg²⁺ and Cr³⁺ on dead biomass Mango (Mangifera indica) and Neem (Azadirachta indica) bark has been assessed at micro to tracer level concentrations from aqueous solutions employing the `radiotracer technique'. A high level of uptake of metal ions on these solid surfaces occurs within ca. 4 h of contact time reaching apparent saturation. The increase of sorptive concentration (10⁻⁸ to 10⁻² mol dm⁻³), temperature (293–323 K) and pH (ca. 3 to 10) favoured the removal process of these ions; but in the case of Hg²⁺ on Neem bark, there was seemingly no temperature effect. The uptake process follows first order rate law and obeys the Freundlich adsorption isotherm. Added anions and cations in the bulk solution inhibit to some extent the removal of these toxic ions. Similarly the inhibition in the uptake was also observed when both biomasses were irradiated by neutron and γ-rays prior to being employed as sorbents. No significant sorption of Cd²⁺ was observed on these dead biomass solid surfaces under various physical–chemical conditions.     

MRI in characterization of focal liver lesions: Comparison of T2 weighting by conventional spin-echo and turbo spin-echo sequences

Forty-one patients with 61 proved focal liver lesions underwent MRI of the liver at 1.0 T, with the aim of evaluating the usefulness of turbo spin-echo (TSE) sequences in characterizing focal liver lesions, by comparing them with conventional spin-echo (CSE) sequences. Two different TSE protocols were employed, with constant echo time and varying repetition time: TSE-S (3000 msec) and TSE-L (5100 msec). All images were evaluated quantitatively (signal-to-noise ratio ‘SNR’) and qualitatively: because benign lesions were all liquid (12 cysts and 10 hemangiomas), they were well characterized morphologically on the basis of signal intensity. Mean SNR was significantly different between metastases and benign lesions (P < .0001) with all T2 sequences. Among the single T2 sequences tested, logistic regression analysis showed TSE-L to have the best predictive ability of the nature of focal lesions, with a G value of 42.02, compared to 29.87 of TSE-S and 25.55 of CSE second echo (SE II). The combination of TSE-L with TSE-S did not modify these results, whereas the combination of TSE-L with CSE only resulted in slight improvement (G = 46.95). Comparison of the receiver operating characteristic (ROC) curves showed only SE II (area under the ROC curve of .8312) to be significantly inferior to the best single sequence, or TSE-L (area under the ROC curve of .9176; P = .027). All sequences were equivalent in qualitative evaluation, with good reproducibility, sensitivity ranging from .94 to 1.0, and specificity ranging from .86 to .93. This study confirms the value of TSE sequences in characterization of focal liver lesions. Time of acquisition is strongly reduced with these sequences, whereas results are fairly similar to those obtained with CSE. TSE sequences could therefore replace CSE for the study of focal liver lesions.