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1.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-38885878

RESUMO

Ankle fractures represent up to 9% of all fractures, with an increased incidence in the elderly population. Among these fractures, isolated fractures of the lateral malleolus are the most common, representing 65-70% of all cases. The therapeutic decision-making primarily relies on the stability of the ankle ring, considering it stable if affected at one point and unstable if two or more points are affected. Surgical treatment focuses on restoring the length of the fibula, joint reconstruction, stabilizing the syndesmosis, and providing a stable fixation. It is crucial to rule out associated injuries that may influence therapeutic management. This article reviews the evaluation and management of lateral malleolus fractures, proposes a decision-making algorithm, and examines several fibular fixation options.

2.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-38754732

RESUMO

INTRODUCTION AND OBJECTIVES: A Consensus document on the management of patients with neurogenic detrusor overactivity (NDO) was published in 2018. The present document aims to update its recommendations regarding treatment considering the new evidence available, and to contribute to the standardization of the management of this disorder. METHODS: The methodology used was based on a systematic review and the Nominal Group Technique. The clinical coordinator (CC) and the Consensus update group (CUG) defined the questions to be updated and carried out a systematic review to identify the new available evidence. After being evaluated by the expert panel, the relevant recommendations were updated and agreed in a consensus meeting. RESULTS: A total of 3210 publications were identified and 26 publications that met the inclusion criteria were included. The CUG updated 18 recommendations on the therapeutic approach to NDO. Unanimous consensus was reached on all of them. CONCLUSIONS: Previous recommendations need to be revised due to the availability of new drugs, the increasing evidence on the use of botulinum toxin or neuromodulation procedures, and new surgical options.

3.
Artigo em Inglês | MEDLINE | ID: mdl-38431048

RESUMO

Eosinophilia in not an uncommon findings in the intensive care unit (ICU); however, DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms) syndrome, which is characterized by a hypersensitivity reaction to drugs and manifests as eosinophilia, systemic involvement and maculopapular erythematous rash 2-6 weeks after exposure to the offending drug, is an exceptional occurrence. We present the first case described in the literature of DRESS syndrome with pulmonary involvement in the form of interstitial pneumonitis and persistent adult respiratory distress syndrome (ARDS) secondary to proton pump inhibitors (PPI). The patient made a good recovery after withdrawal of the offending drug and long-term treatment with systemic corticosteroids. We also present a systematic review of all cases of DRESS with pulmonary involvement in the form of interstitial pneumonitis and cases of PPI-induced DRESS published to date; none of these describe pulmonary involvement.

4.
Eur Urol Focus ; 2023 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-37973453

RESUMO

CONTEXT: The complications of synthetic midurethral slings (MUSs) in women with stress urinary incontinence (SUI) have become a globally debated issue. OBJECTIVE: To systematically review the short- and long-term complications of mesh slings reported in observational data compared with clinical trial data, to determine whether the complication rates from clinical trials reflects "real-world" observational data. EVIDENCE ACQUISITION: PubMed and Cochrane Library were searched. Methods as detailed in Preferred Reporting Items for Systematic Reviews and Meta-analyses and Cochrane Handbook for Systematic Reviews of Interventions were followed. EVIDENCE SYNTHESIS: Thirty registries/databases including 709 335 MUS procedures (1-22 yr of follow-up) were identified. MUS procedures were associated with intraoperative bladder perforation in 0.86-3.6%, urethral perforation in 0-0.1%, vascular injury in 0.04-0.1%, voiding lower urinary tract symptoms (LUTS) in 1.47-3.5%, vaginal exposure in 0.2-1.9%, and reoperation in up to 9% of cases. Forty-three randomised clinical trials were identified, including 6284 women who underwent MUS procedures and 2177 women who underwent other interventions (1-10 yr of follow-up). MUS procedures were associated with urinary tract perforation in 2.58%, vaginal injury in 1.43%, de novo voiding LUTS in 4.37%, de novo storage LUTS in 5.41%, mesh extrusion/exposure (vaginal/urinary tract) in 2.54%, dyspareunia in 2.26%, pain (pelvic/suprapubic/perineal) in 2.83%, and reoperation for complications required in 1.82% of cases. Meta-analyses of the randomised controlled trials revealed that retropubic MUSs were associated with more events of urinary tract perforation (risk ratio [RR] 9.81, 95% confidence interval [CI] 5.05-19.04, high certainty of evidence [COE]) and voiding LUTS (RR 1.57, 95% CI 1.19-2.07, high COE) than transobturator MUSs. MUSs were associated with more events of pain than mini-slings (RR 1.72, 95% CI 1.04-2.87, moderate COE). CONCLUSIONS: Short- and long-term data on complications of polypropylene mesh used for female SUI are fairly comparable when using outcome data from well-designed clinical trials or from less structured prospective or retrospective registries. Comparisons have to be made with caution since the two systems of data collection are inherently incomparable. This knowledge should be incorporated in the discussion on how to implement polypropylene mesh for female stress incontinence. PATIENT SUMMARY: In order to know whether mesh tapes used for treating stress incontinence work well and are safe, high-quality information is important. It appears that well-designed clinical studies give similar results to large registration databases. These data should be interpreted with caution in view of the different ways the information was collected. These results will help physicians and patients understand the risks of mesh tapes.

5.
bioRxiv ; 2023 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-37461525

RESUMO

Loss of proteostasis is a hallmark of aging and Alzheimer disease (AD). Here, we identify ß-hydroxybutyrate (ßHB), a ketone body, as a regulator of protein solubility in the aging brain. ßHB is a small molecule metabolite which primarily provides an oxidative substrate for ATP during hypoglycemic conditions, and also regulates other cellular processes through covalent and noncovalent protein interactions. We demonstrate ßHB-induced protein insolubility across in vitro, ex vivo, and in vivo mouse systems. This activity is shared by select structurally similar metabolites, is not dependent on covalent protein modification, pH, or solute load, and is observable in mouse brain in vivo after delivery of a ketone ester. Furthermore, this phenotype is selective for pathological proteins such as amyloid-ß, and exogenous ßHB ameliorates pathology in nematode models of amyloid-ß aggregation toxicity. We have generated a comprehensive atlas of the ßHB-induced protein insolublome ex vivo and in vivo using mass spectrometry proteomics, and have identified common protein domains within ßHB target sequences. Finally, we show enrichment of neurodegeneration-related proteins among ßHB targets and the clearance of these targets from mouse brain, likely via ßHB-induced autophagy. Overall, these data indicate a new metabolically regulated mechanism of proteostasis relevant to aging and AD.

6.
Int J Biol Macromol ; 242(Pt 3): 124883, 2023 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-37201890

RESUMO

The light-induced processes performed by photofunctional polymer films are crucial aspects of developing integrated energy storage devices properly. Herein, we report the preparation, characterization, and study of the optical properties of a series of biobased cellulose acetate/azobenzene (CA/Az1) handleable films at different compositions. The photoswitching/back-switching behavior of the samples was investigated using varied LED irradiation sources. Additionally, poly(ethylene glycol) (PEG) was deposited onto cellulose acetate/azobenzene films to study the back-switching process's effect and nature in the fabricated films. Interestingly, the melting enthalpies of PEG before and after being irradiated with blue LED light were 2.5 mJ and 0.8 mJ, respectively. Conveniently, FTIR and UV-visible spectroscopy, thermogravimetry (TGA), contact angle, differential scanning calorimetry (DSC), polarized light microscopy (PLM), and atomic force microscopy (AFM) were used for the characterization of the sample films. Complementarily, theoretical electronic calculations provided a consistent approach to the energetic change in the dihedral angles and non-covalent interaction for the trans and cis isomer in the presence of cellulose acetate monomer. The results of this study revealed that CA/Az1 films are viable photoactive materials displaying handleability attributes with potential uses in harvesting, converting, and storing light energy.


Assuntos
Luz , Raios Ultravioleta , Celulose/química
7.
Sci Rep ; 13(1): 7507, 2023 05 09.
Artigo em Inglês | MEDLINE | ID: mdl-37160959

RESUMO

Opioids have been used to manage pain for thousands of years, but they have significant potential for abuse. Prescription opioids, like oxycodone, are associated with 32% of overdoses, that have reached a total of 75,673 deaths in 2021. A major challenge is maximizing their therapeutic potential while minimizing the negative side effects including opioid use disorder (OUD). The Ketogenic Diet (KD) has been reported to reduce pain and decrease the severity of alcohol use disorder, yet its effects on oxycodone responses remain unknown. KD mice displayed increased oxycodone-induced locomotor activity and enhanced antinociceptive effects of oxycodone, suggesting a dietary effect on opiate sensitivity. Male KD mice exposed to chronic oxycodone exhibited increased naloxone-induced jumps, suggesting a sex-specific effect of diet on opioid withdrawal. Consistent with this, male KD mice self-administered less oxycodone while female KD mice did not differ from controls. Finally, no effect of KD on motivation to obtain oxycodone was observed during a progressive ratio schedule. These data suggest sex-biased effects of KD on responses to opioids that should be considered and potentially leveraged in both clinical pain management and treatment of OUD.


Assuntos
Alcoolismo , Dieta Cetogênica , Transtornos Relacionados ao Uso de Opioides , Feminino , Masculino , Animais , Camundongos , Oxicodona/farmacologia , Analgésicos Opioides/farmacologia , Dor , Agitação Psicomotora
8.
Rev. argent. dermatol ; 104: 61-70, ene. 2023. graf
Artigo em Espanhol | LILACS-Express | LILACS | ID: biblio-1529614

RESUMO

Resumen La enfermedad de Fox-Fordyce (EFF) es un trastorno inflamatorio crónicopoco frecuente de las glándulas apocrinas. Afecta comúnmente a mujeres entre los 13-35 años. Su etiopatogenia es multifactorial. Se caracteriza por pápulas foliculares pruriginosas dispuestas en zonas que contienen las glándulas mencionadas. Se presenta el caso clínico de una paciente de 30 años, con pápulas foliculares en axilas compatibles con enfermedad de Fox-Fordyce. El propósito deeste trabajo es presentar una entidad infrecuente y brindar una revisión bibliográfica repasando los diagnósticos diferenciales y las opciones terapéuticas disponibles.


Abstract Fox-Fordyce disease (FFD) is a rare chronic inflammatory disorder of the apocrine glands. It commonly affects women between 13-35 years. Its etiopathogenesis is multifactorial. This disorder is characterized by pruritic follicular papules arranged in areas containing the aforementioned glands. We reporta clinical case of a 30-year-old female patient, with follicular papules on armpits compatible with Fox-Fordyce disease. The purpose of this paper is to report a uncommon entity while providing a bibliographical revision highlighting the differential diagnoses and their available therapeutic options.

9.
Rev. argent. dermatol ; 103(4): 21-30, dic. 2022. graf
Artigo em Espanhol | LILACS-Express | LILACS | ID: biblio-1431483

RESUMO

Resumen El carcinoma escamoso (CEC) es un tumor maligno de la epidermis y sus anexos. Es el segundo en frecuencia después del carcinoma basocelular y presenta distintas variantes clinicopatológicas. El subtipo carcinoma verrucoso (CV) es una variante poco frecuente de CEC con características histopatológicas y comportamiento específico. Ocasionalmente, se pueden observar componentes carcinomatosos de células escamosas convencionales en el CV, denominándose a esta entidad tumores "híbridos", los cuales representan el 20% de los casos observados. Reportamos el caso de un paciente varón de 72 años con una gran lesión exofítica que compromete 5to dedo y planta de pie derecho con diagnóstico de carcinoma escamoso híbrido. El objetivo de la presentación es mostrar una asociación infrecuente, haciendo énfasis en su seguimiento cercano ya que puede manifestar cambios en su comportamiento clínico diseminándose a los ganglios linfáticos regionales.


Abstract Squamous carcinoma (SCC) is a malignant tumor of the epidermis and its appendages. It is the second most common after basal cell carcinoma and has different clinicopathological variants. The verrucous carcinoma (VC) subtype is a rare variant of SCC with histopathological characteristics and specific behavior. Occasionally, carcinomatous components of conventional squamous cells can be observed in the VC, this entity being called "hybridized" tumors, which represent 20% of cases.We report the case of a 72-year-old male with a large exophytic lesion involving the 5th right toe and foot with a diagnosis of squamous hybrid carcinoma. The objective of the presentation is to show an infrequent association, emphasizing its close follow-up as it can modify its clinical behavior by spreading to regional lymphnodes.

10.
J Chem Phys ; 157(8): 084308, 2022 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-36050017

RESUMO

X-ray photodesorption yields of N215 and CO13 are derived as a function of the incident photon energy near the N (∼400 eV) and O K-edge (∼500 eV) for pure N215 ice and mixed CO13:N215 ices. The photodesorption spectra from the mixed ices reveal an indirect desorption mechanism for which the desorption of N215 and CO13 is triggered by the photoabsorption of CO13 and N215, respectively. This mechanism is confirmed by the x-ray photodesorption of CO13 from a layered CO13/N215 ice irradiated at 401 eV on the N 1s → π* transition of N215. This latter experiment enables us to quantify the relevant depth involved in the indirect desorption process, which is found to be 30-40 monolayers in that case. This value is further related to the energy transport of Auger electrons emitted from the photoabsorbing N215 molecules that scatter toward the ice surface, inducing the desorption of CO13. The photodesorption yields corrected from the energy that can participate in the desorption process (expressed in molecules desorbed by eV deposited) do not depend on the photon energy; hence, they depend neither on the photoabsorbing molecule nor on its state after Auger decay. This demonstrates that x-ray induced electron stimulated desorption, mediated by Auger scattering, is the dominant process explaining the desorption of N215 and CO13 from the ices studied in this work.


Assuntos
Elétrons , Fótons , Raios X
11.
Rev. argent. dermatol ; 103(2): 41-50, jun. 2022. graf
Artigo em Espanhol | LILACS-Express | LILACS | ID: biblio-1431473

RESUMO

Resumen El granuloma actínico es una dermatosis granulomatosa poco frecuente, que se observa en adultos de mediana edad con antecedentes de fotoexposición. Su patogénesis no es clara; siendo la teoría más aceptada la radiación solar como factor disparador. Se caracteriza por placas anulares con atrofia central y bordes eritematosos elevados que son similares a los observados en el granuloma anular. Se presenta el caso clínico de una paciente de 71 años, con placas anulares en antebrazos compatibles con granuloma actínico. Se comunica el caso por lo infrecuente de esta entidad y se realiza una revisión bibliográfica.


Abstract Actinic granuloma is a rare granulomatous dermatosis, seen in middle-aged adults with a history of photoexposure. Its pathogenesis is not clear; the most accepted theory being solar radiation as a triggering factor. It is characterized by annular plaques with central atrophy and raised erythematous borders that are similar to those seen in granuloma annulare. The clinical case of a 71-year-old patient with annular plaques on the forearms compatible with actinic granuloma is presented. The case is reported due to the infrequent nature of this entity and a bibliographical review is carried out.

12.
J Vet Cardiol ; 41: 154-164, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35364502

RESUMO

INTRODUCTION: Systemic administration of tissue plasminogen activator (tPA) is seldomly reported in dogs and cats. ANIMALS: Client-owned animals receiving tPA (2010-2020). MATERIALS AND METHODS: Medical records of dogs and cats receiving tPA for distant known/suspected thrombus were reviewed. Fourteen dog visits (24 injections) and five cat visits (six injections) were included. RESULTS: Canine known/suspected thrombus included pulmonary thromboembolism (n=6), intracardiac thrombus (n=4), aortic thrombus (n=1), cranial vena cava thrombus (n=2), and femoral and iliac veins thrombus (n=1). Various canine primary diseases were represented, but open-heart surgery was the most common cause. Median time between diagnosis/suspicion of thrombus and tPA injection was 24.5 h (range, 3-150 h). Mean total tPA dose was 1.0±0.78 mg/kg. Clinical improvement occurred in 93% of dogs. Non-fatal complications were reported in 14% of dogs. Dogs' survival to discharge was 78.6% without identifiable non-survivor characteristics. Feline known/suspected thrombus included unilateral feline aortic thromboembolism (FATE) (n=2), bilateral FATE (n=2), and right renal artery thrombus. Feline primary diseases included cardiomyopathy (n=5). Median time between diagnosis/suspicion of thrombus and tPA injection was 4 h (range, 2-17 h) and median total tPA dose was 1.0 mg/kg (range, 0.6-1.4 mg/kg).Clinical improvement occurred during 40% of the visits. All cats (n=3) with acute kidney injury (AKI) at admission developed worsening AKI and reperfusion injury. Of the remaining two visits, one developed a non-fatal AKI. Cats' survival to discharge was 40%. CONCLUSIONS: Systemic thrombolysis with tPA seems to be effective and safe in dogs. More investigation is needed in cats.


Assuntos
Doenças do Gato , Doenças do Cão , Terapia Trombolítica , Trombose , Ativador de Plasminogênio Tecidual , Animais , Doenças do Gato/tratamento farmacológico , Gatos , Doenças do Cão/tratamento farmacológico , Cães , Estudos Retrospectivos , Terapia Trombolítica/veterinária , Trombose/tratamento farmacológico , Trombose/veterinária , Ativador de Plasminogênio Tecidual/uso terapêutico , Resultado do Tratamento
13.
Ind Eng Chem Res ; 61(3): 1332-1343, 2022 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-35110829

RESUMO

The reduction of CO2 emissions and its elimination from the atmosphere has become one of the major problems worldwide, since CO2 is the main cause of the greenhouse effect and climate change. In recent years, a great number of carbonaceous materials that can be used as CO2 adsorbents have been synthesized. The strategy is usually to synthesize the materials and determine their adsorption capacity without studying previously the factors that influence this capacity. In this work, different properties of the adsorbents are analyzed to study their influence on the CO2 adsorption capacity. For this purpose, 10 adsorbents have been synthesized using different strategies and characterized with X-ray photoelectron spectroscopy, X-ray diffraction, and micro-Raman spectroscopy. The percentage of sp2 carbons, the position of the D + D' peak of the second-order Raman spectrum, the micropore volume, and the grain size of the C sp2 domains have been related to the amount of CO2 adsorbed by the adsorbents. The results confirm a linear relationship between the volume of the micropores and the CO2 uptake and it proves that CO2 retention is favored in those materials that, in addition to having a high volume of micropores, also have low grain size of C.

14.
Artigo em Inglês | MEDLINE | ID: mdl-34995899

RESUMO

BACKGROUND: Obesity is a worldwide public health problem characterized by fat tissue accumulation, favouring adipose tissue and metabolic alterations. Increasing energy expenditure (EE) through brown adipose tissue activation and white adipose tissue (WAT) browning has gained relevance as a therapeutic approach. Different bioactive compounds, such as n-3 polyunsaturated fatty acids (PUFA), have been shown to induce those thermogenic effects. This process is regulated by the gut microbiota as well. Nevertheless, obesity is characterized by gut microbiota dysbiosis, which can be restored by weight loss and n-3 PUFA intake, among other factors. Knowledge gap: However, the role of the gut microbiota on the n-3 PUFA effect in inducing thermogenesis in obesity has not been fully elucidated. OBJECTIVE: This review aims to elucidate the potential implications of this interrelation on WAT browning adiposw sittue (BAT), BAT activity, and EE regulation in obesity models.


Assuntos
Ácidos Graxos Ômega-3 , Microbioma Gastrointestinal , Tecido Adiposo Marrom/metabolismo , Tecido Adiposo Branco/metabolismo , Metabolismo Energético , Ácidos Graxos Ômega-3/metabolismo , Humanos , Obesidade/metabolismo , Termogênese
15.
Earths Future ; 10(12): e2022EF003061, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37035442

RESUMO

Sea-level rise and associated flood hazards pose severe risks to the millions of people globally living in coastal zones. Models representing coastal adaptation and impacts are important tools to inform the design of strategies to manage these risks. Representing the often deep uncertainties influencing these risks poses nontrivial challenges. A common uncertainty characterization approach is to use a few benchmark cases to represent the range and relative probabilities of the set of possible outcomes. This has been done in coastal adaptation studies, for example, by using low, moderate, and high percentiles of an input of interest, like sea-level changes. A key consideration is how this simplified characterization of uncertainty influences the distributions of estimated coastal impacts. Here, we show that using only a few benchmark percentiles to represent uncertainty in future sea-level change can lead to overconfident projections and underestimate high-end risks as compared to using full ensembles for sea-level change and socioeconomic parametric uncertainties. When uncertainty in future sea level is characterized by low, moderate, and high percentiles of global mean sea-level rise, estimates of high-end (95th percentile) damages are underestimated by between 18% (SSP1-2.6) and 46% (SSP5-8.5). Additionally, using the 5th and 95th percentiles of sea-level scenarios underestimates the 5%-95% width of the distribution of adaptation costs by a factor ranging from about two to four, depending on SSP-RCP pathway. The resulting underestimation of the uncertainty range in adaptation costs can bias adaptation and mitigation decision-making.

16.
Chaos ; 32(12): 123141, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36587316

RESUMO

A derivation of the diffusion equation is presented using the maximum caliber principle and the continuity equation for a system composed of paths traveled by a free particle in a time interval. By identifying the diffusion coefficient in the obtained diffusion equation, it is shown that there is an inverse proportionality relationship concerning the particle's mass so that a higher mass is related to lower diffusion, and the lower mass is connected to the higher diffusion. This relationship is also shown using Monte Carlo simulations to sample the path space for a free particle system and then using the time slicing equation to obtain the probability of the particle position for each time showing the diffusion behavior for different masses.

17.
Sci Rep ; 11(1): 23078, 2021 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-34845293

RESUMO

Dehydration of the oceanic subducting slab promotes the formation of magmatic arcs, intra-slab intermediate-depth seismicity, and hydration of the overlying mantle wedge. However, the complex permeability structure of the overriding plate controls the magma and fluid migration and their accumulation at shallower depths. In this regard, mapping the inner structure of the overriding crust and mantle is crucial to understand the magmatic and hydrological processes in subduction zones. We integrate 3-D P-wave, [Formula: see text], and electrical resistivity tomographic models of the northern Chilean subduction zone to map the magmatic and fluids derived from the subducting oceanic Nazca plate. Results show a continental crust relatively thick (50-65 km) characterized by a lower zone of high [Formula: see text] values (7.2-7.6 km/s), which is interpreted as the presence of plutonic rocks. The mantle lithospheric wedge is weakly hydrated ([Formula: see text] = 1.75-1.8) while the forearc continental crust is traversed by regions of reduced electrical resistivity values ([Formula: see text] [Formula: see text]) interpreted as zones of relatively high permeability/fracturing and fluid content. These regions spatially correlate with upper plate trans-lithospheric deformation zones. Ascending melts accumulate preferentially in the back-arc, whereas hydrothermal systems form trenchward of the volcanic arc. The results highlight the complex permeability structure of the upper South American plate.

18.
Int J Biol Macromol ; 193(Pt A): 258-268, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34655589

RESUMO

Novel biobased films consisting of alginate blends with poly (octanoic acid 2-thiophen-3-yl-ethyl ester) (POTE), a conducting polymer, were prepared by solution casting, and their optical, morphological, thermal, and surface properties were studied. Using UV-visible spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM), the effects of tetrahydrofuran solvent vapors on the optical properties and surface morphology of biobased films with different POTE contents were studied. Results indicate that morphological rearrangements of POTE take place during the process of solvent exposure. Specifically, the solvent vapor induced the formation of POTE small crystalline domains, which allows envisioning the potential of tuning UV-visible absorbance and wettability behavior of biobased films. Finally, theoretical electronic calculations (specifically frontier molecular orbitals analysis) provided consistent evidence on POTE's preferential orientation and selectivity toward the THF-vapor medium.


Assuntos
Alginatos/química , Polímeros/química , Solventes , Propriedades de Superfície , Molhabilidade
20.
Appl Radiat Isot ; 177: 109913, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34450415

RESUMO

KMgF3 fluoroperovskite doped with thulium at different concentrations were synthesized by the solid-state reaction method. The phase composition and the thermal stability up to 600 °C of the polycrystals were analyzed by X-ray diffraction and thermogravimetric analysis, respectively. The KMgF3 at 1.0 mol% of Tm polycrystals showed the best thermal stability and did not present another phase. The gamma radiation (0.1-10 kGy) effect in thulium-doped KMgF3 produced the F color centers, and their aggregates such as F2, and F3 centers. The F centers, and the potassium vacancies (VK-) in the fluoroperosvkites were analyzed by the optical absorption and emission measurements. Optical absorption at 275 nm and 443 nm were assigned to F and F2, respectively, in undoped KMgF3. Tm-doped fluoroperovskite shows the optical absorption bands at 277, 393, 432, and 577 nm, which were ascribed to the F, F3, F2 and VK- centers, respectively. When the F band for undoped polycrystals was excited at 275 nm, a clear emission associated with F2 and F3 centers was observed. In the case of Tm-doped, an enhancement of the blue emission at 457 nm occurred and a UV band (354 nm) was observed upon exciting the F band. The blue emission of thulium was overlapped with the F3 color center band. The emission bands at 457 and 354 nm were ascribed to 1D2 - 3F4 and 1D2 - 3H6 transitions of Tm in KMgF3. The optical absorption and glow curves were investigated too. The glow curves were assisted by the color centers, vacancies, and thulium impurity. Thermal bleaching shows that the F center was the main participant to give rise to the TL intensity of the glow curves. Thulium acts as a deep electron trap in the bandgap of the KMgF3 fluoroperovskites forming TL peak at the higher temperature, from 430 to 408 °C. The absorption, emission, and thermoluminescence glow peaks of the undoped and Tm-doped KMgF3 were compared.

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