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Ethanol (EtOH) intake and noise exposure are particularly concerning among human adolescents because the potential to harm brain. Unfortunately, putative underlying mechanisms remain to be elucidated. Moreover, implementing non-pharmacological strategies, such as enriched environments (EE), would be pertinent in the field of neuroprotection. This study aims to explore possible underlying triggering mechanism of hippocampus-dependent behaviors in adolescent animals of both sexes following ethanol intake, noise exposure, or a combination of both, as well as the impact of EE. Adolescent Wistar rats of both sexes were subjected to an intermittent voluntary EtOH intake paradigm for one week. A subgroup of animals was exposed to white noise for two hours after the last session of EtOH intake. Some animals of both groups were housed in EE cages. Hippocampal-dependent behavioral assessment and hippocampal oxidative state evaluation were performed. Results show that different hippocampal-dependent behavioral alterations might be induced in animals of both sexes after EtOH intake and sequential noise exposure, that in some cases are sex-specific. Moreover, hippocampal oxidative imbalance seems to be one of the potential underlying mechanisms. Additionally, most behavioral and oxidative alterations were prevented by EE. These findings suggest that two frequently found environmental agents may impact behavior and oxidative pathways in both sexes in an animal model. In addition, EE resulted a partially effective neuroprotective strategy. Therefore, it could be suggested that the implementation of a non-pharmacological approach might also potentially provide neuroprotective advantages against other challenges. Finally, considering its potential for translational human benefit might be worth.
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Etanol , Hipocampo , Ruído , Ratos Wistar , Animais , Hipocampo/efeitos dos fármacos , Masculino , Feminino , Etanol/administração & dosagem , Etanol/toxicidade , Ruído/efeitos adversos , Ratos , Consumo de Bebidas Alcoólicas , Caracteres Sexuais , Estresse Oxidativo/efeitos dos fármacos , Estresse Oxidativo/fisiologiaRESUMO
The forensically important genus Thanatophilus Leach, 1815 (Coleoptera: Silphidae) is a widespread group of carrion beetles that occupies the Holarctic and Afrotropical realms. It has recently received more recognition, as its species are frequently detected on large carrion, including humans, and can be useful in estimating the time of colonization (TOC) and the post-mortem interval (PMI). The immature stages of Thanatophilus sinuatus (Fabricius, 1775) were reared on three different meat diets (pork liver, pork muscle, and chicken muscle). Diet influence on some of the essential life history traits of the species was examined for different populations. Our findings indicated an accelerated development on pork muscle followed closely by pork liver and a prolonged development on chicken muscle. The diet significantly affected the size, and the body condition (weight/ size) as both pork muscle and liver produced individuals in better physical condition (larger and heavier). The impact of two cyclic photoperiod regimes (16 h Light (L): 8 h Dark (D) and 12 h L: 12 h D) was further evaluated and indicated no significant variability.
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Besouros , Humanos , Animais , Comportamento Alimentar , Reprodução , DietaRESUMO
INTRODUCTION AND AIMS: Endoscopy is the most effective method for identifying gastric adenocarcinoma (GAC). Interval gastric cancer (IGC) is GAC that is diagnosed 2-3 years after a normal endoscopy. Its characteristics are unknown in the Colombian environment. The clinical, histopathologic, and endoscopic characteristics were evaluated, along with the presentation rate, proton pump inhibitor (PPI) use, and IGC survival rate, and compared with other types of GAC. METHODS: A retrospective, analytic study was conducted on a prospective cohort. It evaluated 513 patients with GAC treated at our institution, within the time frame of January 2012 and June 2018. The patients had endoscopic diagnosis of GAC and endoscopy within the past three years that was negative for tumor. RESULTS: A total of 513 patients diagnosed with GAC were evaluated. Forty-two of the patients had IGC (8.2%): 9 early lesions and 33 advanced lesions (79%). The IGCs were smaller (31 vs. 41 mm; P < .01), as well as flatter and more depressed (P < .01). There was no association with PPI use, but there was an association with a history of gastrectomy and anastomosis (P = .02), as well as the absence of red flags (P < .003). The most frequent locations were the gastric body (52%) and the antrum (26%). Overall two-year survival was similar between IGC and GAC (37.1 vs. 39.3%, P = .72). CONCLUSION: A total of 8.2% of recently diagnosed GAC were cases of IGC. The presence of anastomosis and the absence of red flags were related to IGC. Overall survival was poor and there were no differences from the other types of GAC detected.
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Neoplasias Gástricas , Humanos , Neoplasias Gástricas/patologia , Estudos Retrospectivos , Estudos Prospectivos , Gastroscopia/métodosRESUMO
INTRODUCTION: The analysis of the core biomarkers of Alzheimer's Disease (AD) in the cerebrospinal fluid (CSF) is recommended in the clinical units where it is available. Because of the absence of universal validated values, the determination of specific cut-off points for each center and its population is recommended. The main objective of the CORCOBIA study was to determine the cut-off points of core AD CSF biomarkers for several centers (Parc de Salut Mar, Barcelona and Hospital General de Granollers), which work with the same reference laboratory (Laboratori de Referència de Catalunya). METHODS: Prospective study including cognitively unimpaired individuals (CU, n = 42), subjects with amnestic mild cognitive impairment (aMCI, n = 35) and patients with dementia due to Alzheimer's Disease (AD, n = 48), in whom clinical and neuropsychological assessment, neuroimaging, APOE genotyping and lumbar puncture to analyse amyloid beta peptides (Aß42, Aß40), total tau (tTau) and phosphorylated Tau (pTau181) using the Lumipulse G600II (Fujirebio) was performed. The values of sensitivity (SE), specificity (SP), predictive values and area under the curve (AUC) were calculated, determining the cut-off point according to the Youden index by comparing the CU and AD groups. RESULTS: The resulting cut-offs and their AUC were the following: Aß42 750 pg/mL (AUC 0.809); Aß42/Aß40 0.062 (AUC 0.78); pTau181 69.85 pg/mL (AUC 0.81); tTau 522.0 pg/mL (AUC 0.79); Aß42/tTau 1.76 (AUC 0.86); Aß42/pTau181 10.25 (AUC 0.86). CONCLUSIONS: The determination of cut-off points of core AD CSF biomarkers for the participating centers allows a better diagnostic accuracy. The ratio CSF Aß42/pTau181 shows the highest AUC and better balance between sensitivity and specificity.
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OBJECTIVE: Peroxisome proliferator-activated receptor alpha (PPARα) is a nuclear transcription factor with a role in gene expression changes associated to lipid metabolism. PPARα polymorphic variants have been previously correlated to serum lipid profile but in Mexico, there is no previous report about that association. For this reason, the aim of this study was to investigate the relationship between PPARα polymorphic variants and lipids level in serum in a Mexican population. PATIENTS AND METHODS: Two-hundred and forty women from the Northeast region of Mexico were included in the study. Anthropometric characteristics and serum lipid profile (such as triglycerides, total cholesterol, LDL cholesterol and HDL cholesterol) were evaluated. Genomic DNA extraction and purification were made from blood samples. Real-time PCR and TaqMan probes were used for genotyping of rs1800206 and rs4253778 single nucleotide polymorphisms (SNPs). RESULTS: Linear regression analysis (adjusted by age and body mass index (BMI)) showed a significant statistical association of rs4253778 with total cholesterol (p=0.034) and LDL cholesterol (p=0.037). Any significant association was found between rs1800206 and lipid levels. CONCLUSIONS: These results suggested that rs4253778 (C allele) is associated with high levels of total cholesterol and LDL in a Mexican women population.
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PPAR alfa/genética , Polimorfismo de Nucleotídeo Único , HDL-Colesterol , LDL-Colesterol , Feminino , Genótipo , Humanos , México/epidemiologia , TriglicerídeosRESUMO
Coleoptera are currently considered a fundamental tool to help solve criminal investigations, allowing forensic entomologists to estimate post-mortem intervals and obtain other ecology-related information. Thanatophilus rugosus (Linnaeus, 1758) is an important necrophagous beetle distributed through most of the Palaearctic region, where it is readily found on human bodies and animal carcasses. In this study, the new thermal summation models for all the developmental stages of Thanatophilus rugosus are provided. Beetles were reared at six different constant and ecologically relevant temperatures (12, 14, 16, 18, 20, and 22 °C), and their developmental times were measured. Thermal summation constants were calculated for each developmental stage (egg, three larval instars, post-feeding stage, and pupa).
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Besouros/crescimento & desenvolvimento , Entomologia Forense/métodos , Animais , Comportamento Alimentar , TemperaturaRESUMO
Patients with chronic spinal cord injury suffer from a number of pathophysiological alterations that can lead to important morbidity and mortality in the perioperative period. The diaphragmatic pacemaker is a device that enables pulmonary ventilation in patients with high cervical cord injuries and provides them with a better quality of life when compared to mechanical ventilation. We present here the clinical case of a patient with chronic spinal cord injury who used a diaphragmatic pacemaker, and who was scheduled for percutaneous nephrolithotomy and double-J stent implantation. The anesthesiologist should know the pathophysiological situation of these patients in order to provide a safe perioperatory care.
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Marca-Passo Artificial , Traumatismos da Medula Espinal , Diafragma , Humanos , Qualidade de Vida , Respiração Artificial , Traumatismos da Medula Espinal/complicações , Traumatismos da Medula Espinal/terapiaRESUMO
The role of lymphocytes and their main subsets as prognostic factors of death in SARS-CoV-2-infected patients remains unclear, with no information obtained from patients outside China. We aimed to assess whether measuring lymphocyte subpopulations added clinical value to the total lymphocyte counting regarding mortality when they were simultaneously tested at hospital admission. Peripheral blood was analysed in 701 polymerase chain reaction (PCR)-confirmed consecutive patients by lysed-no washed flow cytometry. Demographic and clinical features were registered in electronic medical records. Statistical analysis was performed after a 3-month follow-up. The 112 patients who died were older and had significantly higher frequencies of known co-morbidities than survivor COVID-19 patients. A significant reduction in total lymphocytes, CD3+ , CD4+ , CD8+ and CD19+ counts and CD3+ percentage was found in the group of deceased patients (P < 0·001), while the percentage of CD56+ /CD16+ natural killer (NK) cells was significantly higher (P < 0·001). Multivariate logistic regression analysis showed a significantly increased risk of in-hospital death associated to age [odds ratio (OR) = 2·36, 95% confidence interval (CI) = 1·9-3·0 P < 0·001]; CD4+ T counts ≤ 500 cells/µl, (OR = 2·79, 95% CI = 1·1-6·7, P = 0·021); CD8+ T counts ≤ 100 cells/µl, (OR = 1·98, 95% CI = 1·2-3·3) P = 0·009) and CD56+ /CD16+ NK ≥ 30%, (OR = 1·97, 95% CI = 1·1-3·1, P = 0·002) at admission, independent of total lymphocyte numbers and co-morbidities, with area under the curve 0·85 (95% CI = 0·81-0·88). Reduced counts of CD4+ and CD8+ T cells with proportional expansion of NK lymphocytes at admission were prognostic factors of death in this Spanish series. In COVID-19 patients with normal levels of lymphocytes or mild lymphopenia, imbalanced lymphocyte subpopulations were early markers of in-hospital mortality.
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Antígenos CD/sangue , Linfócitos T CD4-Positivos/metabolismo , Linfócitos T CD8-Positivos/metabolismo , COVID-19 , Mortalidade Hospitalar , SARS-CoV-2/metabolismo , Subpopulações de Linfócitos T/metabolismo , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Contagem de Linfócito CD4 , COVID-19/sangue , COVID-19/mortalidade , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , EspanhaRESUMO
INTRODUCTION: Narcolepsy is the second most common sleep disorder. It is characterised by excessive daytime sleepiness together with other symptoms such as cataplexy, sleep paralysis, and hallucinations. The pathophysiology and treatment of this disease, together with its associated syndromes, can severely interfere with anaesthesia. METHODOLOGY: Due to the lack of quality evidence on which to base a high grade of recommendation for anaesthesia in these patients, we performed a non-systematic, narrative review of the literature in Pubmed. We used the descriptors narcolepsy, anesthesia, surgery, perioperative, opioid, obstructive, apnea and sleep both individually and with AND and OR connectors. CONCLUSION: The recommendation to avoid opioids and the stability of opioid-free anaesthesia (OFA) make this approach an option to consider in these patients. We describe a case in which it was used safely.
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Anestesia , Cataplexia , Narcolepsia , Paralisia do Sono , Analgésicos Opioides/efeitos adversos , Cataplexia/diagnóstico , Humanos , Narcolepsia/diagnósticoRESUMO
Introducción: Las amebas de vida libre (AVL) Naegleria fowleri, Acanthamoeba spp., Balamuthia mandrillaris, son protozoos ampliamente distribuidos en la naturaleza. Son microorganismos oportunistas, que afectan preferentemente al sistema nervioso central causando cuadros de meningoencefalitis amebiana primaria o de encefalitis granulomatosa amebiana (EGA), ambas patologías de alta mortalidad. Descripsión del Caso: Paciente femenina de 10 años, que ingresa a nuestro hospital por presentar hemiparesia braquiocrural izquierda, vómitos y cefalea de 72 horas de evolución. Se realiza tomografía computada y Resonancia Magnética en la que se identifica una lesión expansiva, sólido-quística ubicada en la región fronto derecha. Se realiza exéresis completa de la misma y se implementa tratamiento farmacológico lográndose la restitución ad-integrum de la función motora y la resolución de la EGA a 30 meses de seguimiento. Discusión: La encefalitis granulomatosa amebiana es una patología causada por amebas de vida libre. Su presentacíon clínica puede ser indistinguible de otras causas de leptomeningitis o encefalitis, como las de origen bacteriano, viral o por micobacterias lo que impide conocer su real incidencia. Su tratamiento antiparasitario es muy complejo y su evolución es habitualmente fatal. Conclusión: Reportamos un caso de Encefalitis Amebiana Granulomatosa en una paciente pediátrica inmunocompetente, con excelente evolución.
Introduction: Free-living amoebas (FLA) Naegleria fowleri, Acanthamoeba spp., and Balamuthia mandrillaris, are protist widely distributed in nature. Are opportunistic microorganisms, preferentially affect the central nervous system causing primary amoebic meningoencephalitis or amoebic granulomatous encephalitis (AGE), both with high mortality. Case report: A 10 year-old female patient was admitted with a three-day history of left hemiparesis accompanied with headaches and vomiting. Computed tomography and magnetic resonance were performed, in which an expansive solid cystic mass was observed in the right fronto-parietal region. Complete resection was performed and pharmacological treatment was started, achieving complete restitution of motor function and resolution of AGE after 30 months of follow-up. Discussion: AGE is a desease caused by free-living amoebas. Its clinical presentation is similar to other leptomeningitis or encephalitis of different etiology such as bacterial, viral or by mycobacterial, which cannot know its real incidence. Its pharmacological treatment is complex and its evolution is usually fatal. Conclusion: We report a case of Amoebic Granulomatous Encephalitis in an immunocompetent pediatric patient with good outcome.
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Encefalite , Pediatria , Acanthamoeba , TomografiaRESUMO
RESUMEN El granuloma anular es un trastorno relativamente frecuente, se desconoce la prevalencia exacta, tiene mayor frecuencia en niños y adultos jóvenes. Se caracteriza por pequeñas pápulas agrupadas, en configuración anular, a menudo con distribución simétrica y acra. La mayor parte los casos se resuelve en forma espontánea dentro de los 2 años, pero la tasa de recidivas es del 40%. Presentamos el caso clínico de una paciente de 72 años de edad con granuloma anular diseminado, tratado con pentoxifilina, con buen resultado terapéutico.
ABSTRACT Annular granuloma is a relatively frequent disorder, the exact prevalence is unknown, it is more frequent in children and young adults. It is characterized by small grouped papules, in annular configuration, often with symmetric and acrid distribution. Most cases resolve spontaneously within 2 years, but the recurrence rate is 40%. We present the clinical case of a 72-year-old patient with disseminated annular granuloma, treated with pentoxifylline, with good therapeutic results.
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Stereolithography is an additive manufacturing technology commonly used to build either prototypes or final parts. Nevertheless, the manufacture of structural parts has been ruled out owing to the poor mechanical properties of conventional UV-curable resins. Moreover, the inventory of available commercial resins is still limited and they exhibit low thermal and electrical conductivity values. In this work, some composite materials were designed using Al microparticles dispersed within an SLA commercial resin matrix. These composites overcame the difficulties caused by the light scattering effect during the photopolymerisation process in the SLA technology. Dispersion of the filler was characterised by means of SEM/EDX and AFM. The composites exhibited improved thermal and mechanical behaviour in comparison with the pristine resin. The simplicity of the synthesis method used to prepare the composites provides a convenient starting point to explore new ways of designing composites for SLA with improved mechanical and functional properties.
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BACKGROUND: Patients subjected to bariatric surgery present a greater risk of complications due to the use of opioids. The goal is to evaluate the security and suitability of the Opioid Free Anaesthesia (OFA) protocol implemented in the Hospital Universitario Virgen de la Victoria in 2018. METHOD: Prospective study carried out on 38 patients subjected to laparoscopic bariatric surgery under the OFA protocol in the year 2018 at the H.U. Virgen de la Victoria (Málaga, Spain). Variables were gathered to establish haemodynamic control and perioperative pain, which were analysed using Stata v.16. RESULTS: The average age was 43 years, the average body mass index was 48.14 and the average stay in the operating theatre was 178 minutes. Control of hypertensive response following laryngoscopy occurred in 88.1% of the cases. On entering the Post Anaesthesia Care Unit (PACU), SpO2 without a supplementary contribution in the transfer showed a median of 97% with p75 = 95%, while the p75 of pain evaluation by means of Visual Analogue Scale (VAS) was 3, with 68% of patients without pain. On discharge from the PACU, all presented VAS below 4 and it was only necessary to administer a low dose of Pethidine in seven patients. CONCLUSION: The OFA has proved to be secure and achieves optimum pain control. In the reconverted cases, good control of the parameters opens up the possibility of its use in more painful surgeries.
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Anestesia/métodos , Anestésicos/administração & dosagem , Cirurgia Bariátrica/métodos , Laparoscopia , Adulto , Analgésicos Opioides/administração & dosagem , Período de Recuperação da Anestesia , Índice de Massa Corporal , Feminino , Humanos , Hipertensão/epidemiologia , Hipotensão/epidemiologia , Masculino , Pessoa de Meia-Idade , Duração da Cirurgia , Medição da Dor/métodos , Dor Pós-Operatória/diagnóstico , Dor Pós-Operatória/prevenção & controle , Complicações Pós-Operatórias/epidemiologia , Náusea e Vômito Pós-Operatórios/prevenção & controle , Estudos ProspectivosRESUMO
OBJECTIVE: To analyze the relationship between therapeutic (weight-adjusted) dose of bemiparin and anti-Xa activity in patients with venous thromboembolism (VTE) and cancer in comparison with a cohort of patients with VTE without cancer, and its relationship with outcomes. MATERIALS AND METHODS: This is a prospective cohort study that comprised a cohort of patients with cancer-associated VTE and a cohort of non-cancer patients with VTE, all of them treated with bemiparin. The ethics committee approved the study and informed consent was obtained from the patients. RESULTS: One hundred patients were included (52 with cancer and 48 without cancer), with a median follow-up of 9.8 months. Mean anti-Xa activity was 0.89 (± 0.33) UI/mL in oncological patients and 0.83 (± 0.30) UI/mL in non-cancer patients (mean difference - 0.05 95% CI - 0.18; 0.06). A multiple linear regression model showed that anti-Xa peak was associated with the dose/kg independently of possible confounding variables (presence of cancer, age, sex and eGFR-estimated Glomerular Filtration Rate), in a way that for every 1 UI of dose/kg increase, the anti-Xa peak activity increased 0.006 UI/mL (95% CI 0.003; 0.009) (p < 0.001). The predictive capacity of anti-Xa peak in the oncology cohort showed an area under the ROC curve of 0.46 (95% CI 0.24-0.68), 0.70 (95% CI 0.49-0.91) and 0.74 (95% CI 0.44-0.94) for death, first bleeding and recurrence of VTE, respectively, and none was statistically significant. CONCLUSION: In patients with venous thromboembolism treated with bemiparin, anti-Xa levels were not influenced by the presence of cancer.
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Anticoagulantes/uso terapêutico , Inibidores do Fator Xa/sangue , Heparina de Baixo Peso Molecular/uso terapêutico , Neoplasias/complicações , Tromboembolia Venosa/sangue , Idoso , Anticoagulantes/efeitos adversos , Feminino , Hemorragia/induzido quimicamente , Heparina de Baixo Peso Molecular/efeitos adversos , Humanos , Modelos Lineares , Masculino , Neoplasias/sangue , Estudos Prospectivos , Insuficiência Renal/diagnóstico , Tromboembolia Venosa/tratamento farmacológico , Tromboembolia Venosa/etiologiaRESUMO
Sub-monolayer (SML) deposition of InSb within InAs matrix by migration enhanced epitaxy tends to form type II SML nanostructures offering efficient light emission within the mid-infrared (MIR) range between 3 and 5 µm. In this work, we report on the Sb distribution in InSb/InAs SML nanostructures with InAs cap layers grown at temperatures lower than that associated with the under-grown InSb active layer. Analysis by transmission electron microscopy (TEM) in 002 dark field conditions shows that the reduction in the growth temperature of the InAs cap layer increases the amount of Sb deposited in the layers, in good agreement with the x-ray diffraction results. TEM micrographs also show that the layers are formed by random InSbAs agglomerates, where the lower cap temperature leads to a more continuous InSb layer. Quantitative atomic column resolved high angle annular dark field-scanning (S)TEM analyses also reveal atomic columns with larger composition of Sb for the structure with the lowest InAs cap layer temperature. The dependence of the Sb distribution on InAs cap growth temperature allows tuning the corresponding emission wavelength in the MIR range, as shown by the photoluminescence emission spectra.
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INTRODUCTION AND AIM: Abdominal pain in children is a frequent cause of emergency room consultation. An important group of those patients presents with chronic constipation and fecal impaction. Plain abdominal x-ray is widely used for making a diagnosis and ruling out the need for surgical treatment. The present study examined the association between pain intensity and fecal impaction grade. MATERIALS AND METHODS: An analytic cross-sectional study was conducted that compared 2 radiographic scales to determine the association between the grade of fecal impaction observed and abdominal pain intensity in patients that sought medical attention at an emergency service within a 7-month period. The analysis was carried out by 2 different observers, utilizing 2 different radiographic scales to confirm their reproducibility. The degree of interobserver agreement was measured using the Kappa coefficient and the association between abdominal pain and fecal impaction grade was measured through the Spearman correlation coefficient. RESULTS: There was a significant association between pain intensity and the radiographic grade of fecal impaction (P<.05) for the radiographic scale by segments and its interobserver agreement was high, compared with the scale by percentage. CONCLUSIONS: Radiographic scales may be useful in the evaluation and treatment of patients with abdominal pain and constipation. The segmental scale showed less interobserver variability, suggesting its proposal as an alternative in the evaluation and follow-up of patients with chronic constipation.
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Dor Abdominal/etiologia , Constipação Intestinal/complicações , Impacção Fecal/complicações , Impacção Fecal/diagnóstico por imagem , Adolescente , Criança , Pré-Escolar , Estudos Transversais , Serviços Médicos de Emergência , Feminino , Humanos , Lactente , Masculino , RadiografiaRESUMO
InSb/InAs sub-monolayer (SML) nanostructures such as SML quantum dots offer sharper emission spectra, a better modal gain and a larger modulation bandwidth compared to its Stranski-Krastanov counterpart. In this work, the Sb distribution of SML InSb layers grown by migration enhanced epitaxy has been analyzed by transmission electron microscopy (TEM) techniques. The analysis of the material by diffraction contrast in 002 dark field conditions and by atomic column resolved high angle annular dark field-scanning TEM reveal the presence of a low Sb content InSbAs continuous layer with scarce Sb-rich InSbAs agglomerates. The intensity profiles obtained by both techniques point to Sb segregation during growth. This segregation has been quantified using the Muraki segregation model obtaining a high segregation coefficient R of 0.81 towards the growth direction. The formation of a continuous InSbAs wetting layer as a result of a SML deposition of Sb on the InAs surface is discussed.
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This work reports on the design and development of nanocomposites based on a polymeric matrix containing biodegradable Polylactic Acid (PLA) and Polyhydroxyalkanoate (PHA) coated with either Graphite NanoPlatelets (GNP) or silver nanoparticles (AgNP). Nanocomposites were obtained by mechanical mixing under mild conditions and low load contents (<0.10 wt %). This favours physical adhesion of the additives onto the polymer surface, while the polymeric bulk matrix remains unaffected. Nanocomposite characterisation was performed via optical and focused ion beam microscopy, proving these nanocomposites are selectively modified only on the surface, leaving bulk polymer unaffected. Processability of these materials was proven by the fabrication of samples via injection moulding and mechanical characterisation. Nanocomposites showed enhanced Young modulus and yield strength, as well as better thermal properties when compared with the unmodified polymer. In the case of AgNP coated nanocomposites, the surface was found to be optically active, as observed in the increase of the resolution of Raman spectra, acquired at least 10 times, proving these nanocomposites are promising candidates as surface enhanced Raman spectroscopy (SERS) substrates.
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Lead halide (APbX3) perovskites, in polycrystalline thin films but also perovskite nanoparticles (NPs) has demonstrated excellent performance to implement a new generation of photovoltaic and photonic devices. The structural characterization of APbX3 thin films using (scanning) transmission electron microscopy ((S)TEM) techniques can provide valuable information that can be used to understand and model their optoelectronic performance and device properties. However, since APbX3 perovskites are soft materials, their characterization using (S)TEM is challenging. Here, we study and compare the structural properties of two different metal halide APbX3 perovskite thin films: bulk CH3NH3PbI3 prepared by spin-coating of the precursors in solution and CsPbBr3 colloidal NPs synthetized and deposited by doctor blading. Both specimen preparation methods and working conditions for analysis by (S)TEM are properly optimized. We show that CH3NH3PbI3 thin films grown by a one-step method are composed of independent grains with random orientations. The growth method results in the formation of tetragonal perovskite thin films with good adherence to an underlying TiO2 layer, which is characterized by a photoluminescence (PL) emission band centered at 775 nm. The perovskite thin films based on CsPbBr3 colloidal NPs, which are used as the building blocks of the film, are preserved by the deposition process, even if small gaps are observed between adjacent NPs. The crystal structure of CsPbBr3 NPs is cubic, which is beneficial for optical properties due to its optimal band gap. The absorption and PL spectra measured in both the thin film and the colloidal solution of CsPbBr3 NPs are very similar, indicating a good homogeneity of the thin films and the absence of aggregation of NPs. However, a particular care was required to avoid long electron irradiation times during our structural studies, even at a low voltage of 80 kV, as the material was observed to decompose through Pb segregation.
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The influence of the neighbouring atomic-columns in determining the composition at atomic column scale of quaternary semiconductor compounds, using simulated HAADF-STEM images is evaluated. The InAlAsSb alloy, a promising material in the photovoltaic field, is considered. We find that the so called 'crosstalk' effect plays an important role for the aimed compositional determination. The intensity transfer is larger from neighbouring atomic columns with higher average Z, and towards atomic columns with smaller Z. Our results show that in order to obtain precise information on the column composition, the HAADF-STEM intensities of both columns need to be taken into account simultaneously.