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1.
Crit Rev Clin Lab Sci ; 58(3): 207-224, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33929278

RESUMO

In the clinical laboratory, knowledge of and the correct use of clot activators and anticoagulant additives are critical to preserve and maintain samples in optimal conditions prior to analysis. In 2017, the Latin America Confederation of Clinical Biochemistry (COLABIOCLI) commissioned the Latin American Working Group for Preanalytical Phase (WG-PRE-LATAM) to study preanalytical variability and establish guidelines for preanalytical procedures to be applied by clinical laboratories and health care professionals. The aim of this critical review, on behalf of COLABIOCLI WG-PRE-LATAM, is to provide information to understand the mechanisms of the interactions and reactions that occur between blood and clot activators and anticoagulant additives inside evacuated tubes used for laboratory testing. Clot activators - glass, silica, kaolin, bentonite, and diatomaceous earth - work by surface dependent mechanism whereas extrinsic biomolecules - thrombin, snake venoms, ellagic acid, and thromboplastin - start in vitro coagulation when added to blood. Few manufacturers of evacuated tubes state the type and concentration of clot activators used in their products. With respect to anticoagulant additives, sodium citrate and oxalate complex free calcium and ethylenediaminetetraacetic acid chelates calcium. Heparin potentiates antithrombin and hirudin binds to active thrombin, inactivating the thrombin irreversibly. Blood collection tubes have improved continually over the years, from the glass tubes containing clot activators or anticoagulant additives that were prepared by laboratory personnel to the current standardized evacuated systems that permit more precise blood/additive ratios. Each clot activator and anticoagulant additive demonstrates specific functionality, and both manufacturers of tubes and laboratory professional strive to provide suitable interference-free sample matrices for laboratory testing. Both manufacturers of in vitro diagnostic devices and laboratory professionals need to understand all aspects of venous blood sampling so that they do not underestimate the impact of tube additives on laboratory testing.


Assuntos
Anticoagulantes , Coleta de Amostras Sanguíneas , Anticoagulantes/farmacologia , Coagulação Sanguínea , Humanos , Flebotomia
2.
J Eur Acad Dermatol Venereol ; 35(9): 1865-1873, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34013600

RESUMO

BACKGROUND: Descriptions of cutaneous findings associated with COVID-19 have not been consistently accompanied by histopathology or confirmatory testing for SARS-CoV-2. OBJECTIVE: To describe and classify the cutaneous findings with supporting histopathology of confirmed COVID-19 inpatients. METHODS: We included consecutive inpatients with a confirmed diagnosis of COVID-19 for whom a dermatology consult was requested. A skin biopsy was performed in all cases. Skin findings were classified as being compatible with a cutaneous manifestation of COVID-19 or as representing a distinct clinical entity. RESULTS: Twenty-eight patients were studied in whom thirty-one dermatologic diagnoses were made. Twenty-two of the dermatoses were compatible with a cutaneous manifestation of COVID-19; nine entities were not associated with infection by SARS-CoV-2. The most common COVID-19-associated pattern was an exanthematous presentation. In four patients, a new pattern was observed, characterized by discrete papules with varied histopathological findings including a case of neutrophilic eccrine hidradenitis. No cases of pernio-like lesions were identified. Skin findings not associated with COVID-19 represented 29% of diagnoses and included Malassezia folliculitis, tinea, miliaria and contact dermatitis. LIMITATIONS: There is no gold-standard test to distinguish between viral exanthems and drug reactions. CONCLUSION: A histopathological study is critical before attributing skin findings to a manifestation of COVID-19.


Assuntos
COVID-19 , Pérnio , Dermatopatias , Humanos , SARS-CoV-2 , Pele
3.
Curr Cardiol Rep ; 23(6): 63, 2021 05 07.
Artigo em Inglês | MEDLINE | ID: mdl-33961137

RESUMO

PURPOSE OF REVIEW: In this review article we will discuss the acute hypertensive response in the context of acute ischemic stroke and present the latest evidence-based concepts of the significance and management of the hemodynamic response in acute ischemic stroke. RECENT FINDINGS: Acute hypertensive response is considered a common hemodynamic physiologic response in the early setting of an acute ischemic stroke. The significance of the acute hypertensive response is not entirely well understood. However, in certain types of acute ischemic strokes, the systemic elevation of the blood pressure helps to maintain the collateral blood flow in the penumbral ischemic tissue. The magnitude of the elevation of the systemic blood pressure that contributes to the maintenance of the collateral flow is not well established. The overcorrection of this physiologic hemodynamic response before an effective vessel recanalization takes place can carry a negative impact in the final clinical outcome. The significance of the persistence of the acute hypertensive response after an effective vessel recanalization is poorly understood, and it may negatively affect the final outcome due to reperfusion injury. Acute hypertensive response is considered a common hemodynamic reaction of the cardiovascular system in the context of an acute ischemic stroke. The reaction is particularly common in acute brain embolic occlusion of large intracranial vessels. Its early management before, during, and immediately after arterial reperfusion has a repercussion in the final fate of the ischemic tissue and the clinical outcome.


Assuntos
Isquemia Encefálica , AVC Isquêmico , Acidente Vascular Cerebral , Pressão Sanguínea , Circulação Cerebrovascular , Humanos
4.
Med Oral Patol Oral Cir Bucal ; 25(5): e668-e674, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32851984

RESUMO

BACKGROUND: The objective of this study was to describe the bacterial communities associated with pediatric patients with endodontic infections of temporal teeth by targeting the 16S rRNA gene using pyrosequencing. MATERIAL AND METHODS: Microbiological samples were obtained from the lower primary molars of thirteen 13 pediatric patients with dental infections. An aspiration method for microbiological sampling was used. The identification of microbiota employing the pyrosequencing method by targeting the 16S gene was performed. RESULTS: Ribosomal 16S RNA gene sequences were amplified, obtaining a total of 16,182 sequences from 13 primary infected molars (13 different individuals) by pyrosequencing. Bacteroidetes phyla (35.15%) were the most abundant followed by Firmicutes (33.3%) and Fusobacteria (10.05%); the presence of specific pathogenic bacteria was determined as well. CONCLUSIONS: The infected root canal of primary teeth contains a high diversity of anaerobic bacteria, and Bacteroidetes, Firmicutes, and Fusobacteria phyla were the most abundant; Prevotella and Streptococcus genera were the most prevalent.


Assuntos
Bactérias , Bacteroidetes/genética , Criança , Humanos , RNA Ribossômico 16S , Análise de Sequência de DNA , Dente Decíduo
5.
J Food Sci Technol ; 56(9): 4045-4056, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31477976

RESUMO

In this work, mint essential oil (MEO) was added into gelatin films and antifungal activity was evaluated. Five concentrations of MEO (0, 0.06, 0.13, 0.25, 0.38, 0.50% (g/g gelatin)) were incorporated into gelatin solutions. The films were prepared by casting and characterized for their barrier properties, mechanical resistance, morphology, thermal and antifungal activity. The addition of oil into the solution slightly improved water vapor barrier, increased thickness and opacity, decreased transparency and modified thermal and mechanical properties of films. With addition of oil above 0.38%, the films were effective against the growth of Botrytis cinerea and Rhizopus stolonifer, indicating an inhibitory activity. Thus, gelatin-based edible films incorporated with MEO showed to be an effective way to inhibit microbial growth on the film surface.

7.
Med Vet Entomol ; 32(3): 271-281, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29368343

RESUMO

An ecological analysis of a tick (Ixodida: Ixodidae) community across a landscape gradient presenting differential anthropogenic disturbance in the Atlantic Forest ecoregion in Argentina was performed. Ticks were collected from vegetation and hosts between September 2014 and August 2016. A total of 12 697 free-living ticks and 3347 specimens from hosts were collected, including 317 ticks infesting humans. The values obtained show considerable species diversity in the forest environment accompanied by low equitability. The similarity index derived from a comparison of forest and agricultural environments was higher than that calculated by comparing forest and urban environments. The data suggest that although a cycle of one generation per year is apparent in some species, more than one cohort may co-exist within the populations of some of these species. Well-marked patterns of the seasonal distribution of free-living tick species emerged in environments with no anthropic modification. The results indicate that forest environments are more suitable habitats than agricultural and urban environments for many species of native tick, but are unsuitable for exotic species that have successfully established in environments that have been modified by man.


Assuntos
Biodiversidade , Ecossistema , Ixodidae/fisiologia , Infestações por Carrapato/epidemiologia , Infestações por Carrapato/veterinária , Animais , Argentina , Doenças das Aves/epidemiologia , Doenças das Aves/parasitologia , Aves , Florestas , Humanos , Mamíferos , Prevalência , Infestações por Carrapato/parasitologia
8.
Mol Biol Evol ; 33(12): 3054-3064, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27604223

RESUMO

Two-component signaling (TCS) is the primary means by which bacteria sense and respond to the environment. TCS involves two partner proteins working in tandem, which interact to perform cellular functions whereas limiting interactions with non-partners (i.e., cross-talk). We construct a Potts model for TCS that can quantitatively predict how mutating amino acid identities affect the interaction between TCS partners and non-partners. The parameters of this model are inferred directly from protein sequence data. This approach drastically reduces the computational complexity of exploring the sequence-space of TCS proteins. As a stringent test, we compare its predictions to a recent comprehensive mutational study, which characterized the functionality of 204 mutational variants of the PhoQ kinase in Escherichia coli We find that our best predictions accurately reproduce the amino acid combinations found in experiment, which enable functional signaling with its partner PhoP. These predictions demonstrate the evolutionary pressure to preserve the interaction between TCS partners as well as prevent unwanted cross-talk. Further, we calculate the mutational change in the binding affinity between PhoQ and PhoP, providing an estimate to the amount of destabilization needed to disrupt TCS.


Assuntos
Bactérias/genética , Bactérias/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Transdução de Sinais/genética , Sequência de Aminoácidos , Simulação por Computador , Regulação Bacteriana da Expressão Gênica , Fenótipo , Ligação Proteica , Proteínas Quinases/metabolismo , Análise de Sequência de Proteína/métodos
9.
Photochem Photobiol Sci ; 16(6): 854-860, 2017 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-28492632

RESUMO

One-dimensional titanate nanotubes (H2Ti2O5·H2O) functionalized with silver nanoparticles (AgNPs) exhibited unique properties for the effective inactivation of the Gram-negative Escherichia coli within 45 minutes under irradiation using a 65 W halogen lamp. The pathway of the photo-assisted catalytic inactivation was examined by SEM and TEM using a reproducible biological protocol for sample preparations. The membrane integrity of the bacteria was damaged due to the oxidative stress caused by the reactive oxygen species, the bacteriostatic effect of the highly-dispersed-surface AgNPs (∼5 nm) and the sharp nanotube penetration that induced the cell death.


Assuntos
Antibacterianos/farmacologia , Escherichia coli/efeitos dos fármacos , Escherichia coli/efeitos da radiação , Nanotubos/química , Prata/farmacologia , Titânio/farmacologia , Antibacterianos/química , Testes de Sensibilidade Microbiana , Processos Fotoquímicos , Prata/química , Titânio/química
11.
Allergol Immunopathol (Madr) ; 45(1): 82-86, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-27789066

RESUMO

BACKGROUND: The Hyper-immunoglobulin M syndromes (HIGM) are a heterogeneous group of genetic disorders, which have been rarely reported to be associated with growth hormone deficiency (GHD). METHODS AND RESULTS: A nine-year-old girl with recurrent urinary tract infections, diarrhoea, sinopulmonary infections, and failure to thrive since the age of six months had normal CD3+, CD4+, CD8+T lymphocytes, and CD19+B lymphocytes and natural killer (NK) cells, but extremely elevated IgM and significantly decreased IgG and IgA. In view of the patient's short stature, growth hormone evaluation was carried out and growth hormone deficiency established. The patient underwent Ig replacement therapy and received growth hormone therapy in addition to antibiotics and responded well. Furthermore, the patient developed benign cervical lymphadenopathy, as well as elevated erythrocyte sedimentation rate, positive autoantibodies to SSA-Ro, and severely dry eyes, which partially responded to both the punctate occlusion and systemic corticosteroids, at the age of seven years. Sequencing analysis of the exons from activation-induced cytidine deaminase (AICDA) gene revealed that the patient was homozygous for a single T to C transversion at position 455 in exon 4, which replaces a Valine with an Alanine. CONCLUSIONS: To our knowledge, this is a new AICDA mutation, which has not been reported previously in HIGM. The mutation analysis could improve diagnosis of HIGM patients and also elaborating on the spectrum of AICDA mutations.


Assuntos
Citidina Desaminase/genética , Nanismo Hipofisário/genética , Hormônio do Crescimento/uso terapêutico , Síndrome de Imunodeficiência com Hiper-IgM/genética , Mutação de Sentido Incorreto/genética , Corticosteroides/uso terapêutico , Autoimunidade/genética , Criança , Análise Mutacional de DNA , Feminino , Genótipo , Terapia de Reposição Hormonal , Humanos , Imunoglobulina M/sangue , Lactente , Irã (Geográfico) , Linhagem , Fenótipo
12.
Lupus ; 25(7): 741-8, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-26923285

RESUMO

BACKGROUND: Patients with systemic lupus erythematosus (SLE) have a higher risk for cardiovascular disease (CVD), not fully explained by the conventional risk factors. These patients have endothelial dysfunction (ED) as an early process of atherosclerosis, which can be reversed with therapy. OBJECTIVE: To determine the effect of ezetimibe plus pravastatin on endothelial function in patients with SLE after 12 months of treatment. PATIENTS AND METHODS: An open study, before and after, which assessed the effect of ezetimibe plus pravastatin treatment, was performed. Twenty two patients (21 women and one man) with diagnosis of SLE were studied, with a mean age 40 ± 5 years. Endothelial dysfunction was evaluated using vascular ultrasound of the brachial artery in order to measure the flow-mediated vasodilation (FMV) basal and after 12 months of treatment with pravastatin 40 mg/day plus ezetimibe 10 mg/day. In addition, a lipid profile: total cholesterol (TC), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), and serum C-reactive protein (CRP), was done. RESULTS: We found a basal FMV of 7.58% and 18.22% after 12 months of treatment, with an improvement of 10.64 points 95% CI (7.58-13.58), p < 0.001. TC decreased from 201.3 ± 58.9 mg/dL to 158.06 ± 50.13 mg/dL (p < 0.01); LDL-C from 125.78 ± 44.4 mg/dL to 78.8 ± 32.9 mg/dL (p < 0.001); HDL-C increased from 49.0 ± 16.8 mg/dL to 52.2 ± 13.8 mg/dL (p = 0.077). The basal and final concentrations of CRP were 4.49 and 2.8, respectively, with a mean decrease of 2.11 mg/dL, 95% CI (0.908-3.32), p < 0.002. Both drugs were well tolerated. CONCLUSION: Ezetimibe plus pravastatin significantly improved FMV in patients with SLE, decreasing ED and the lipid profile. This treatment ameliorated an early process of atherosclerosis and a risk factor for CVD.


Assuntos
Anticolesterolemiantes/administração & dosagem , Endotélio Vascular/efeitos dos fármacos , Ezetimiba/administração & dosagem , Lúpus Eritematoso Sistêmico/complicações , Pravastatina/administração & dosagem , Adulto , Anticolesterolemiantes/efeitos adversos , Aterosclerose/prevenção & controle , Artéria Braquial/diagnóstico por imagem , Proteína C-Reativa/análise , Colesterol/sangue , Quimioterapia Combinada , Endotélio Vascular/fisiopatologia , Ezetimiba/efeitos adversos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pravastatina/efeitos adversos , Ultrassonografia , Vasodilatação
14.
Neurologia ; 31(5): 332-43, 2016 Jun.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-23601756

RESUMO

INTRODUCTION: Malignant hemispheric infarction (MHI) is a specific and devastating type of ischemic stroke. It usually affects all or part of the territory of the middle cerebral artery although its effects may extend to other territories as well. Its clinical outcome is frequently catastrophic when only conventional medical treatment is applied. OBJECTIVE: The purpose of this review is to analyse the available scientific evidence on the treatment of this entity. DEVELOPMENT: MHI is associated with high morbidity and mortality. Its clinical characteristics are early neurological deterioration and severe hemispheric syndrome. Its hallmark is the development of space-occupying cerebral oedema between day 1 and day 3 after symptom onset. The mass effect causes displacement, distortion, and herniation of brain structures even when intracranial hypertension is initially absent. Until recently, MHI was thought to be fatal and untreatable because mortality rates with conventional medical treatment could exceed 80%. In this unfavourable context, decompressive hemicraniectomy has re-emerged as a therapeutic alternative for selected cases, with reported decreases in mortality ranging between 15% and 40%. CONCLUSIONS: In recent years, several randomised clinical trials have demonstrated the benefit of decompressive hemicraniectomy in patients with MHI. This treatment reduces mortality in addition to improving functional outcomes.


Assuntos
Edema Encefálico/etiologia , Descompressão Cirúrgica/métodos , Infarto da Artéria Cerebral Média/diagnóstico , Infarto da Artéria Cerebral Média/terapia , Humanos , Infarto da Artéria Cerebral Média/etiologia , Infarto da Artéria Cerebral Média/fisiopatologia , Hipertensão Intracraniana , Imageamento por Ressonância Magnética , Tomografia Computadorizada por Raios X
15.
Br J Dermatol ; 172(2): 412-8, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25597261

RESUMO

BACKGROUND: Itching, burning, numbness and tingling of the skin are frequent reasons for dermatology consultation. We hypothesized that these sensations may be attributable to a small-fibre neuropathy. Sweating, which is mediated by small nerve fibres, may be a surrogate marker of small-fibre neuropathy. OBJECTIVES: To investigate the results of thermoregulatory sweat testing (TST), which depicts and estimates whole-body sweating, in patients with itching, burning, numbness and tingling sensations. METHODS: We retrospectively reviewed the medical records of 227 patients with itching, burning, numbness and tingling sensations involving the skin who were seen at our institution during 2008 and also underwent TST. RESULTS: The mean age of the cohort was 54 years (range 3-89), and 58% were female. In all, 149 patients (66%) had abnormal TST results; in 119 (80%) of these patients the areas of anhidrosis on TST corresponded to their symptomatic areas. For each symptom analysed separately, the area of anhidrosis correlated with the area of symptoms in most patients. CONCLUSIONS: Patients with burning, itching, numbness and tingling have abnormal sweating patterns and often do not sweat in the symptomatic areas. These novel findings suggest that a small-fibre neuropathy may underlie many cutaneous symptoms and that the neuropathy can be estimated using TST.


Assuntos
Hipestesia/etiologia , Hipo-Hidrose/etiologia , Parestesia/etiologia , Doenças do Sistema Nervoso Periférico/complicações , Prurido/etiologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Pré-Escolar , Estudos de Coortes , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Adulto Jovem
16.
Soft Matter ; 11(7): 1259-64, 2015 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-25591813

RESUMO

We report on the ability of two-dimensional protein crystals to induce the formation of homo- and heterotypic multicellular spheroids (MCSs) which resemble the morphology and hierarchical organization of living tissues and tumours. We have systematically studied the influence of the initial cell density and incubation time on the kinetics of spheroid growth and spheroid lifespan. Hereby a novel methodology has been established to produce MCSs on protein-based molecular layers.


Assuntos
Proteínas de Bactérias/química , Esferoides Celulares/metabolismo , Proteínas de Bactérias/farmacologia , Cristalização , Células Hep G2 , Células Endoteliais da Veia Umbilical Humana/efeitos dos fármacos , Células Endoteliais da Veia Umbilical Humana/metabolismo , Humanos , Esferoides Celulares/efeitos dos fármacos , Esferoides Celulares/ultraestrutura
17.
Genet Mol Res ; 14(3): 10905-18, 2015 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-26400318

RESUMO

Alternative phylogenies for the genus Streptococcus have been proposed due to uncertainty about the among-species group relationships. Here, we performed a phylogenetic analysis of the genus Streptococcus, considering all the species groups and also the genomic data accumulated by other studies. Seventy-five species were subjected to a Bayesian phylogenetic analysis using sequences from eight genes (16S rRNA, rpoB, sodA, tuf, rnpB, gyrB, dnaJ, and recN). On the basis of our results, we propose a new Phylogeny for the genus, with special emphasis on the inter-species group level. This new phylogeny differs from those suggested previously. From topological and evolutionary distance criteria, we propose that gordonii, pluranimalium, and sobrinus should be considered as new species groups, in addition to the currently recognized groups of mutans, bovis, pyogenic, suis, mitis, and salivarius.


Assuntos
Streptococcus/classificação , Streptococcus/genética , Teorema de Bayes , Evolução Biológica , Classificação/métodos , DNA Bacteriano/genética , Genoma Bacteriano , Filogenia , Análise de Sequência de DNA , Especificidade da Espécie
18.
Genet Mol Res ; 14(4): 19184-90, 2015 Dec 29.
Artigo em Inglês | MEDLINE | ID: mdl-26782571

RESUMO

Streptococcus is a diverse bacterial lineage. Species of this genus occupy a myriad of environments inside humans and other animals. Despite the elucidation of several of these habitats, many remain to be identified. Here, we explore a methodological approach to reveal unknown bacterial environments. Specifically, we inferred the phylogeny of the Mitis group by analyzing the sequences of eight genes. In addition, information regarding habitat use of species belonging to this group was obtained from the scientific literature. The oral cavity emerged as a potential, previously unknown, environment of Streptococcus massiliensis. This phylogeny-based prediction was confirmed by species-specific polymerase chain reaction (PCR) amplification. We propose employing a similar approach, i.e., use of bibliographic data and molecular phylogenetics as predictive methods, and species-specific PCR as confirmation, in order to reveal other unknown habitats in further bacterial taxa.


Assuntos
Teorema de Bayes , Boca/microbiologia , Filogenia , Streptococcus mitis/genética , Streptococcus/genética , Proteínas de Bactérias/genética , DNA Bacteriano/genética , RNA Polimerases Dirigidas por DNA/genética , Bases de Dados de Ácidos Nucleicos , Ecossistema , Humanos , Fator Tu de Elongação de Peptídeos/genética , RNA Ribossômico 16S/genética , Saliva/microbiologia , Análise de Sequência de DNA , Especificidade da Espécie , Streptococcus/classificação , Streptococcus mitis/classificação , Superóxido Dismutase/genética
19.
Clin Neurol Neurosurg ; 240: 108256, 2024 05.
Artigo em Inglês | MEDLINE | ID: mdl-38547629

RESUMO

INTRODUCTION: Ventriculoperitoneal shunt (VPS) infection is a severe complication. Early diagnosis could help to decrease morbidity and treatment costs. Lactate has been used for the diagnosis of other central nervous system infections. The aim of this study is to determine the usefulness of lactate for the diagnosis of VPS infection. METHODOLOGY: Retrospective cohort study. Lactate was measured in patients who consulted with VPS dysfunction between May 2019 and May 2022. Mean were compared according to culture results. A Receiver Operating Characteristic (ROC) curve was performed to determine the appropriate cut-off point. RESULT: Lactate has a high negative predictive value but a low positive predictive value for the diagnosis of ventriculitis.


Assuntos
Ácido Láctico , Derivação Ventriculoperitoneal , Humanos , Derivação Ventriculoperitoneal/efeitos adversos , Estudos Retrospectivos , Feminino , Masculino , Ácido Láctico/líquido cefalorraquidiano , Criança , Pré-Escolar , Lactente , Estudos de Coortes , Adolescente , Ventriculite Cerebral/líquido cefalorraquidiano , Ventriculite Cerebral/diagnóstico
20.
Sci Rep ; 12(1): 797, 2022 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-35039503

RESUMO

A series of gallium arsenide bismide device layers covering a range of growth conditions are thoroughly probed by low-temperature, power-dependent photoluminescence measurements. The photoluminescence data is modelled using a localised state profile consisting of two Gaussians. Good agreement with the raw data is achieved for all layers whilst fixing the standard deviation values of the two Gaussians and constraining the band gap using X-ray diffraction data. The effects of growth temperature and bismuth beam equivalent pressure on the localised state distributions, and other model variables, are both shown to be linked to emission linewidth and device properties. It is concluded that bismuth rich surface conditions are preferable during growth in order to produce the narrowest emission linewidths with this material. These results also show how the growth mode of a gallium arsenide bismide layer can be inferred ex-situ from low-temperature photoluminescence measurements.

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