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1.
Lupus ; 32(9): 1105-1110, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37328161

RESUMO

BACKGROUND: Systemic lupus erythematosus (SLE) is a chronic, systemic, autoimmune disease of multifactorial origin. There are no previous studies in Colombia describing juvenile SLE (jSLE) prevalence, prompting this demographic description. OBJECTIVE: This study aimed for prevalence calculation and epidemiologic analysis of jSLE) in Colombian patients, ages 0-19, from 2015 to 2019. METHODS: This descriptive, cross-sectional study searched the Colombian Ministry of Health database for codes of the International Classification of Diseases, 10th revision (ICD-10) associated with jSLE to estimate the disease prevalence for the total population and for specific age groups at national and regional levels. Calculations used intercensal estimates of population based on the projections of the national statistics administrative department (DANE) from the most recent census. This paper presents a sociodemographic analysis of patients with jSLE. RESULTS: The study identified in Colombia, from 2015 to 2019, 3680 cases with jSLE as the principal diagnosis. Calculated prevalence of jSLE was 25 cases per 100,000 population, with highest frequency in ages 15-19 and females (84%), with a female:male ratio of 5.1:1. CONCLUSION: Estimated prevalence of jSLE in Colombia is at the highest limit of worldwide findings. Consistent with reports in the literature, the disease involves females more frequently than males.


Assuntos
Lúpus Eritematoso Sistêmico , Humanos , Masculino , Feminino , Lúpus Eritematoso Sistêmico/complicações , Colômbia/epidemiologia , Prevalência , Estudos Transversais , Dados de Saúde Coletados Rotineiramente
2.
Clocks Sleep ; 5(2): 249-259, 2023 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-37218866

RESUMO

Sleep disturbances are a common yet often overlooked symptom of psychosis that can drastically affect the quality of life and well-being of those living with the condition. Sleep disorders are common in people diagnosed with schizophrenia and have significant negative effects on the clinical course of the illness and the functional outcomes and quality of life of patients. There is a limited number of studies addressing this question in first-episode psychosis (FEP). In this narrative review, we aimed to provide an overview of sleep disorders in populations with FEP and at-risk mental states (ARMS). The review was focused on the various treatments currently used for sleep disorders, including both non-pharmacological and pharmacological treatments. A total of 48 studies were included. We found that sleep disturbances are associated with attenuated psychotic symptoms and other psychopathological symptoms in ARMSs. The association of sleep disturbances with the transition to psychosis has been poorly investigated. Sleep disturbances have an impact on the quality of life and the psychopathological symptoms of people suffering from FEP. The non-pharmacological treatments include cognitive behavioral therapy for insomnia, bright light therapy, cognitive restructuring techniques, sleep restriction therapy, basic sleep hygiene education, and the provision of portable sleep trackers. Other treatments include antipsychotics in acute phases and melatonin. The early intervention in sleep disturbances may improve overall prognosis in emerging psychosis populations.

3.
Molecules ; 28(8)2023 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-37110832

RESUMO

The impacts on the morphological, electrical and hardness properties of thermoplastic polyurethane (TPU) plates using multi-walled carbon nanotubes (MWCNTs) as reinforcing fillers have been investigated, using MWCNT loadings between 1 and 7 wt%. Plates of the TPU/MWCNT nanocomposites were fabricated by compression molding from extruded pellets. An X-ray diffraction analysis showed that the incorporation of MWCNTs into the TPU polymer matrix increases the ordered range of the soft and hard segments. SEM images revealed that the fabrication route used here helped to obtain TPU/MWCNT nanocomposites with a uniform dispersion of the nanotubes inside the TPU matrix and promoted the creation of a conductive network that favors the electronic conduction of the composite. The potential of the impedance spectroscopy technique has been used to determine that the TPU/MWCNT plates exhibited two conduction mechanisms, percolation and tunneling conduction of electrons, and their conductivity values increase as the MWCNT loading increases. Finally, although the fabrication route induced a hardness reduction with respect to the pure TPU, the addition of MWCNT increased the Shore A hardness behavior of the TPU plates.

5.
Molecules ; 27(23)2022 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-36500440

RESUMO

The rare-earth-free MnAlC alloy is currently considered a very promising candidate for permanent magnet applications due to its high anisotropy field and relatively high saturation magnetization and Curie temperature, besides being a low-cost material. In this work, we presented a simple fabrication route that allows for obtaining a magnetically enhanced bulk τ-MnAlC magnet. In the fabrication process, an electric arc-melting method was carried out to melt ingots of MnAlC alloys. A two-step solution treatment at 1200 °C and 1100 °C allowed us to synthesize a pure room-temperature ε-MnAlC ingot that completely transformed into τ-MnAlC alloy, free of secondary phases, after an annealing treatment at 550 °C for 30 min. The Rietveld refinements and magnetization measurements demonstrated that the quenched process produces a phase-segregated ε-MnAlC alloy that is formed by two types of ε-phases due to local fluctuation of the Mn. Room-temperature hysteresis loops showed that our improved τ-MnAlC alloy exhibited a remanent magnetization of 42 Am2/kg, a coercive field of 0.2 T and a maximum energy product, (BH)max, of 6.07 kJ/m3, which is higher than those reported in previous works using a similar preparation route. Experimental evidence demonstrated that the synthesis of a pure room-temperature ε-MnAlC played an important role in the suppression of undesirable phases that deteriorate the permanent magnet properties of the τ-MnAlC. Finally, magnetic images recorded by Lorentz microscopy allowed us to observe the microstructure and magnetic domain walls of the optimized τ-MnAlC. The presence of magnetic contrasts in all the observed grains allowed us to confirm the high-quality ferromagnetic behavior of the system.


Assuntos
Imãs , Metais Terras Raras , Imãs/química , Ligas/química , Temperatura , Magnetismo
6.
Materials (Basel) ; 15(15)2022 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-35955201

RESUMO

High-purity TiO2 and CuO powders were synthesized by the Pechini method, an inexpensive and easy-to-implement procedure to synthetize metal oxides. The variables of synthesis were the ethylene glycol:citric acid molar ratio and the pH. High reproducibility of the anatase and tenorite phase was obtained for all synthesis routes. The degree of purity of the powders was confirmed by XRD, FTIR, UV-Vis absorption and XPS spectra. SEM and TEM images revealed the powders are composed of micrometer grains that can have a spherical shape (only in the TiO2) or formed by a non-compacted nanocrystalline conglomerate. FTIR spectra only displayed vibrational modes associating TiO2 and CuO with nanoparticle behavior. UV-Vis absorption spectra revealed the values of maximum absorbance percentage of both systems are reached in the ultraviolet region, with percentages above 83% throughout the entire visible light spectrum for the CuO system, a relevant result for solar cell applications. Finally, XPS experiments allow the observation of the valence bands and the calculation of the energy bands of all oxides.

7.
J Wound Care ; 31(4): 356-359, 2022 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-35404703

RESUMO

OBJECTIVE: Martorell hypertensive ischaemic ulcers are often misdiagnosed and can be a clinical and therapeutic challenge. Controversy exists regarding both their underlying triggers and the type of treatment that should be carried out. This study was designed to compare the effectiveness of punch grafting and conventional therapy in pain reduction. METHOD: A single-centre retrospective study was performed, including 40 patients with a clinical diagnosis of a Martorell ulcer or post-traumatic ulcer secondary to arteriolopathy in the elderly, who were treated with punch grafting (n= 24) or conventional medical treatment (n=16). RESULTS: There was a statistically and clinically significant reduction in pain after punch grafting. The minimal overall reduction was of three points in visual analogue pain scores. Of the patients who received punch grafting, 80% reported a VAS pain score of 0 at the third follow-up, in contrast with the 44% (n=4) patients who were treated without punch grafting. The mean time to epithelialisation was 82.1 days in patients who received conventional treatment and 43.5 days in those who received punch grafts. CONCLUSION: Punch grafting is a simple, validated and cost-effective technique that can be performed on an outpatient basis, promotes wound healing and reduces pain. It may control pain and stimulate epithelialisation even if the wound does not present with optimum wound bed characteristics for graft taking. Pain reduction and faster epithelialisation are associated with improvements in patients' quality of life.


Assuntos
Arteriolosclerose , Úlcera da Perna , Úlcera Cutânea , Idoso , Humanos , Úlcera da Perna/cirurgia , Dor , Qualidade de Vida , Estudos Retrospectivos , Transplante de Pele/métodos , Úlcera Cutânea/cirurgia , Úlcera
8.
World J Biol Psychiatry ; 23(6): 464-474, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34856870

RESUMO

OBJECTIVES: Neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), and C-Reactive Protein (CRP) are markers of inflammation that are elevated in bipolar disorder (BD) and are also related to a higher risk of metabolic syndrome (MetS). This study aimed at investigating for the first time the association between NLR, PLR, and CRP and the metabolic status in BD. METHODS: We assessed the association between biomarkers and the metabolic status: number of metabolic risk factors, presence of MetS, insulin sensitivity (Quantitative Insulin Sensitivity Check Index, QUICKI) and insulin resistance (Homeostatic Model Assessment for Insulin Resistance, HOMA-IR index), in a sample of 219 outpatients with BD. RESULTS: 25.9% of the sample met the criteria for MetS. High levels of CRP were found in 12% of the sample. Older age, low PLR, high NLR, and high CRP levels significantly predicted a higher number of MetS risk factors (p < 0.001). Older age and low PLR were associated with a greater likelihood of developing MetS (p = 0.007). CONCLUSIONS: Although further studies are needed to replicate and validate these findings, inflammatory biomarkers as CRP, PLR and NLR could be useful tools to identify patients with a BD at risk for a metabolic adverse outcome.


Assuntos
Transtorno Bipolar , Resistência à Insulina , Síndrome Metabólica , Humanos , Neutrófilos/química , Proteína C-Reativa/análise , Contagem de Plaquetas , Linfócitos , Biomarcadores , Estudos Retrospectivos
9.
Wounds ; 32(8): E38-E41, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33166269

RESUMO

INTRODUCTION: Posttraumatic ulcers secondary to age-related arteriolosclerosis may be included in the clinic-histopathological spectrum of the Martorell hypertensive ischemic ulcer. Histologically, they both present occlusive subcutaneous arteriolosclerosis. Considering these similarities, they could benefit from the same treatment. CASE REPORT: The authors present an 84-year-old white female who had a painful 9-cm x 4-cm ulcer of the central inner aspect of her left leg. The ulcer had developed 2 months prior after mild trauma, with good response to early and sequential punch grafting, combined with single-use negative pressure wound therapy and compression therapy. Pain reduction was obtained from the first punch grafting session. To achieve complete epithelialization 16 weeks after the first punch grafting procedure, 2 more sessions were necessary. CONCLUSIONS: Early punch grafting is an effective technique for pain control and healing promotion in Martorell ulcers. Punch grafting, which may be performed in an outpatient setting, is well tolerated by patients and may be repeated several times if necessary.


Assuntos
Úlcera da Perna/cirurgia , Transplante de Pele/métodos , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Traumatismos da Perna/complicações , Úlcera da Perna/etiologia
10.
Rev. chil. pediatr ; 91(4): 584-590, ago. 2020. tab, graf
Artigo em Espanhol | LILACS | ID: biblio-1138675

RESUMO

INTRODUCCIÓN: El síndrome IPEX (inmunodesregulación, poliendocrinopatía y enteropatía autoinmune ligada a X) causado por mutaciones en el gen FOXP3, se caracteriza por diarrea prolongada, alteraciones endocrinológicas y dermatitis. El tratamiento consiste en la administración de medicamentos inmunosupresores, siendo el trasplante de médula ósea la única cura potencial. OBJETIVO: Describir una nueva mutación del gen FOXP3, así como los hallazgos y evolución de un paciente con síndrome IPEX. CASO CLÍNICO: Lactante menor masculino que debutó al mes de vida con diarrea cró nica, falla intestinal e infecciones recurrentes. Exámenes de laboratorio y biopsia intestinal sugerentes de enteropatía autoinmune. Durante el seguimiento, el paciente presentó refractariedad al manejo inmunosupresor con esteroides, ciclosporina y tacrolimus, falleciendo a los 7 meses de edad por complicaciones vasculares. Antecedente familiar por línea materna de múltiples muertes en hombres menores de 1 año. Ante la sospecha de síndrome IPEX se realizó exoma en trío que reportó una mutación probablemente patogénica en el gen FOXP3. CONCLUSIÓN: Se documentó una nueva mutación del gen FOXP3 en paciente con síndrome IPEX. A pesar de la baja prevalencia de esta enfermedad, es importante el reconocimiento de síntomas no específicos pero sugerentes del diagnóstico.


INTRODUCTION: The IPEX (immune dysregulation, polyendocrinopathy, enteropathy, X-linked) syn drome is caused by the mutations of the FOXP3 gene, characterized by persistent diarrhea, endo crine disorders, and dermatitis. The treatment is the administration of immunosuppressive drugs, where hematopoietic stem cell transplantation is the only potential cure. OBJECTIVE: To describe a new FOXP3 gene mutation, as well as the findings and evolution of a patient with IPEX syndrome. CLINICAL CASE: Male infant presenting at one month of age with chronic diarrhea, intestinal failure, and recurrent infections. Lab tests and intestinal biopsy suggested autoimmune enteropathy. During follow-up, the patient presented resistance to immunosuppressive treatment with corticosteroids, cyclosporine, and tacrolimus, dying at 7 months of age due to vascular complications. He had a ma ternal family history of multiple deaths of men under 1 year of age. IPEX syndrome was suspected therefore a trio whole-exome sequencing was performed that showed a probably pathogenic FOXP3 gene mutation. CONCLUSION: A new FOXP3 gene mutation is reported in a patient with IPEX syndro me. Despite the low prevalence of this disease, it is important to recognize non-specific but suggestive symptoms for its diagnosis.


Assuntos
Humanos , Masculino , Lactente , Doenças Genéticas Ligadas ao Cromossomo X/diagnóstico , Diabetes Mellitus Tipo 1/congênito , Diarreia/diagnóstico , Fatores de Transcrição Forkhead/genética , Doenças do Sistema Imunitário/congênito , Linhagem , Marcadores Genéticos , Doença Crônica , Evolução Fatal , Doenças Genéticas Ligadas ao Cromossomo X/genética , Diabetes Mellitus Tipo 1/diagnóstico , Diabetes Mellitus Tipo 1/genética , Diarreia/genética , Doenças do Sistema Imunitário/diagnóstico , Doenças do Sistema Imunitário/genética , Mutação
11.
Beilstein J Nanotechnol ; 11: 651-661, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32363131

RESUMO

We studied in detail the in-plane magnetic properties of heterostructures based on a ferroelectric BaTiO3 overlayer deposited on a ferromagnetic La2/3Sr1/3MnO3 film grown epitaxially on pseudocubic (001)-oriented SrTiO3, (LaAlO3)0.3(Sr2TaAlO6)0.7 and LaAlO3 substrates. In this configuration, the combination of both functional perovskites constitutes an artificial multiferroic system with potential applications in spintronic devices based on the magnetoelectric effect. La2/3Sr1/3MnO3 single layers and BaTiO3/La2/3Sr1/3MnO3 bilayers using the pulsed-laser deposition technique. We analyzed the films structurally through X-ray reciprocal space maps and high-angle annular dark field microscopy, and magnetically via thermal demagnetization curves and in-plane magnetization versus applied magnetic field loops at room temperature. Our results indicate that the BaTiO3 layer induces an additional strain in the La2/3Sr1/3MnO3 layers close to their common interface. The presence of BaTiO3 on the surface of tensile-strained La2/3Sr1/3MnO3 films transforms the in-plane biaxial magnetic anisotropy present in the single layer into an in-plane uniaxial magnetic anisotropy. Our experimental evidence suggests that this change in the magnetic anisotropy only occurs in tensile-strained La2/3Sr1/3MnO3 film and is favored by an additional strain on the La2/3Sr1/3MnO3 layer promoted by the BaTiO3 film. These findings reveal an additional mechanism that alters the magnetic behavior of the ferromagnetic layer, and consequently, deserves further in-depth research to determine how it can modify the magnetoelectric coupling of this hybrid multiferroic system.

12.
J Wound Care ; 29(3): 194-197, 2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-32160087

RESUMO

OBJECTIVE: Punch-grafting is a traditional technique to enhance wound healing, which has been associated with significant pain reduction. There are few studies measuring pain reduction after punch grafting, our study was designed to measure this outcome. METHOD: Patients with hard-to-heal wounds treated with punch grafting were included in a single centre prospective study. Wound pain intensity was measured using a Visual Analogue Scale (VAS) at baseline (before the procedure) and at three time points after the procedure. Punch grafting was performed in an outpatient setting. Patient demographic data, wound aetiology and percentage of graft take were recorded. RESULTS: A total of 136 patients were included (62 men and 74 women). Mean age was 60±35 years and 51 (38%) had venous leg ulcers (VLU), 29 (21%) had postoperative wounds, 15 (11%) Martorell ulcers, 15 (11%) traumatic wounds, four (3%) arterial ulcers and 22 (16%) 'other' ulcers. Of the patients, 38 (28%) did not present with painful ulcers and, after punch grafting, all of them remained painless; 29 (21%) patients obtained >70% pain reduction, whereas 73 (54%) patients achieved pain suppression. Pain suppression did not depend on the percentage of graft take. CONCLUSION: Punch-grafting is a simple, technique that not only promotes wound healing but also reduces pain. It can also be performed on an outpatient basis. Further studies should be performed to achieve a better understanding of this beneficial finding. Declaration of interest: The authors have no conflicts of interest to declare.


Assuntos
Transplante de Pele , Úlcera Cutânea/cirurgia , Feminino , Humanos , Masculino , Microcirurgia , Pessoa de Meia-Idade , Dor/prevenção & controle , Estudos Prospectivos , Procedimentos de Cirurgia Plástica , Úlcera Cutânea/enfermagem , Resultado do Tratamento , Escala Visual Analógica , Cicatrização
14.
Rev Chil Pediatr ; 91(4): 584-590, 2020 Aug.
Artigo em Espanhol | MEDLINE | ID: mdl-33399737

RESUMO

INTRODUCTION: The IPEX (immune dysregulation, polyendocrinopathy, enteropathy, X-linked) syn drome is caused by the mutations of the FOXP3 gene, characterized by persistent diarrhea, endo crine disorders, and dermatitis. The treatment is the administration of immunosuppressive drugs, where hematopoietic stem cell transplantation is the only potential cure. OBJECTIVE: To describe a new FOXP3 gene mutation, as well as the findings and evolution of a patient with IPEX syndrome. CLINICAL CASE: Male infant presenting at one month of age with chronic diarrhea, intestinal failure, and recurrent infections. Lab tests and intestinal biopsy suggested autoimmune enteropathy. During follow-up, the patient presented resistance to immunosuppressive treatment with corticosteroids, cyclosporine, and tacrolimus, dying at 7 months of age due to vascular complications. He had a ma ternal family history of multiple deaths of men under 1 year of age. IPEX syndrome was suspected therefore a trio whole-exome sequencing was performed that showed a probably pathogenic FOXP3 gene mutation. CONCLUSION: A new FOXP3 gene mutation is reported in a patient with IPEX syndro me. Despite the low prevalence of this disease, it is important to recognize non-specific but suggestive symptoms for its diagnosis.


Assuntos
Diabetes Mellitus Tipo 1/congênito , Diarreia/diagnóstico , Fatores de Transcrição Forkhead/genética , Doenças Genéticas Ligadas ao Cromossomo X/diagnóstico , Doenças do Sistema Imunitário/congênito , Doença Crônica , Diabetes Mellitus Tipo 1/diagnóstico , Diabetes Mellitus Tipo 1/genética , Diarreia/genética , Evolução Fatal , Doenças Genéticas Ligadas ao Cromossomo X/genética , Marcadores Genéticos , Humanos , Doenças do Sistema Imunitário/diagnóstico , Doenças do Sistema Imunitário/genética , Lactente , Masculino , Mutação , Linhagem
16.
Langmuir ; 34(5): 1932-1940, 2018 02 06.
Artigo em Inglês | MEDLINE | ID: mdl-29316786

RESUMO

The integration of high-purity nano-objects on substrates remains a great challenge for addressing scaling-up issues in nanotechnology. For instance, grafting gold nanoparticles (NPs) on zinc oxide films, a major step process for catalysis or photovoltaic applications, still remains difficult to master. We report a modified photodeposition (P-D) approach that achieves tight control of the NPs size (7.5 ± 3 nm), shape (spherical), purity, and high areal density (3500 ± 10 NPs/µm2) on ZnO films. This deposition method is also compatible with large ZnO surface areas. Combining electronic microscopy and X-ray photoelectron spectroscopy measurements, we demonstrate that growth occurs primarily in confined spaces (between the grains of the ZnO film), resulting in gold NPs embedded within the ZnO surface grains thus establishing a unique NPs/surface arrangement. This modified P-D process offers a powerful method to control nanoparticle morphology and areal density and to achieve strong Au interaction with the metal oxide substrate. This work also highlights the key role of ZnO surface morphology to control the NPs density and their size distribution. Furthermore, we experimentally demonstrate an increase of the ZnO photocatalytic activity due to high densities of Au NPs, opening applications for the decontamination of water or the photoreduction of water for hydrogen production.

17.
Langmuir ; 33(41): 11086-11093, 2017 10 17.
Artigo em Inglês | MEDLINE | ID: mdl-28950064

RESUMO

Al/CuO energetic structure are attractive materials due to their high thermal output and propensity to produce gas. They are widely used to bond components or as next generation of MEMS igniters. In such systems, the reaction process is largely dominated by the outward migration of oxygen atoms from the CuO matrix toward the aluminum layers, and many recent studies have already demonstrated that the interfacial nanolayer between the two reactive layers plays a major role in the material properties. Here we demonstrate that the ALD deposition of a thin ZnO layer on the CuO prior to Al deposition (by sputtering) leads to a substantial increase in the efficiency of the overall reaction. The CuO/ZnO/Al foils generate 98% of their theoretical enthalpy within a single reaction at 900 °C, whereas conventional ZnO-free CuO/Al foils produce only 78% of their theoretical enthalpy, distributed over two distinct reaction steps at 550 °C and 850 °C. Combining high-resolution transmission electron microscopy, X-ray diffraction, and differential scanning calorimetry, we characterized the successive formation of a thin zinc aluminate (ZnAl2O4) and zinc oxide interfacial layers, which act as an effective barrier layer against oxygen diffusion at low temperature.

18.
ACS Appl Mater Interfaces ; 8(20): 13104-13, 2016 05 25.
Artigo em Inglês | MEDLINE | ID: mdl-27145017

RESUMO

Nanoenergetic materials are beginning to play an important role in part because they are being considered as energetic components for materials, chemical, and biochemical communities (e.g., microthermal sources, microactuators, in situ welding and soldering, local enhancement of chemical reactions, nanosterilization, and controlled cell apoptosis) and because their fabrication/synthesis raises fundamental challenges that are pushing the engineering and scientific frontiers. One such challenge is the development of processes to control and enhance the reactivity of materials such as energetics of nanolaminates, and the understanding of associated mechanisms. We present here a new method to substantially decrease the reaction onset temperature and in consequence the reactivity of nanolaminates based on the incorporation of a Cu nanolayer at the interfaces of Al/CuO nanolaminates. We further demonstrate that control of its thickness allows accurate tuning of both the thermal transport and energetic properties of the system. Using high resolution transmission electron microscopy, X-ray diffraction, and differential scanning calorimetry to analyze the physical, chemical and thermal characteristics of the resulting Al/CuO + interfacial Cu nanolaminates, we find that the incorporation of 5 nm Cu at both Al/CuO and CuO/Al interfaces lowers the onset temperature from 550 to 475 °C because of the lower-temperature formation of Al-Cu intermetallic phases and alloying. Cu intermixing is different in the CuO/Cu/Al and Al/Cu/CuO interfaces and independent of total Cu thickness: Cu readily penetrates into Al grains upon annealing to 300 °C, leading to Al/Cu phase transformations, while Al does not penetrate into Cu. Importantly, θ-Al2Cu nanocrystals are created below 63% wt Cu/Al, and coexist with the Al solid solution phase. These well-defined θ-Al2Cu nanocrystals seem to act as embedded Al+CuO energetic reaction triggers that lower the onset temperature. We show that ∼10 nm thick Cu at Al/CuO interfaces constitutes the optimum amount to increase both reactivity and overall heat of reaction by a factor of ∼20%. Above this amount, there is a rapid decrease of the heat of reaction.

19.
ACS Appl Mater Interfaces ; 7(22): 11713-8, 2015 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-25988997

RESUMO

In situ deposition of a thin (∼5 nm) layer of copper between Al and CuO layers is shown to increase the overall nanolaminate material reactivity. A combination of transmission electron microscopy imaging, in situ infrared spectroscopy, low energy ion scattering measurements, and first-principles calculations reveals that copper spontaneously diffuses into aluminum layers (substantially less in CuO layers). The formation of an interfacial Al:Cu alloy with melting temperature lower than pure Al metal is responsible for the enhanced reactivity, opening a route to controlling the stochiometry of the aluminum layer and increasing the reactivity of the nanoenergetic multilayer systems in general.

20.
Nano Lett ; 15(1): 492-7, 2015 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-25474731

RESUMO

Epitaxial strain alters the physical properties of thin films grown on single crystal substrates. Thin film oxides are particularly apt for strain engineering new functionalities in ferroic materials. In the case of La(2/3)Ca(1/3)MnO(3) (LCMO) thin films, here we show the first experimental images obtained by electron holography demonstrating that epitaxial strain induces the segregation of a flat and uniform nonferromagnetic layer with antiferromagnetic (AFM) character at the top surface of a ferromagnetic (FM) layer, the whole film being chemical and structurally homogeneous at room temperature. For different substrates and growth conditions the tetragonality of LCMO at room temperature, defined as τ = |c - a|/a, is the driving force for a phase coexistence above an approximate critical value of τC ≈ 0.024. Theoretical calculations prove that the increased tetragonality changes the energy balance of the FM and AFM ground states in strained LCMO, enabling the formation of magnetically inhomogeneous states. This work gives the key evidence that opens a new route to synthesize strain-induced exchanged-biased FM-AFM bilayers in single thin films, which could serve as building blocks of future spintronic devices.

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