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1.
Clin Exp Allergy ; 52(9): 1018-1034, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-35975576

RESUMO

Pollen food syndrome (PFS) is a highly prevalent food allergy affecting pollen-sensitized children and adults. Sufferers experience allergic symptoms when consuming raw plant foods, due to the homology between the pollen allergens and unstable proteins in these foods. The triggers involved can vary depending on the pollen sensitization, which in turn is affected by geographical location. The British Society of Allergy and Clinical Immunology (BSACI) Standards of Care Committee (SOCC) identified a need to develop a guideline for the diagnosis and management of PFS in the United Kingdom (UK). Guidelines produced by the BSACI use either the GRADE or SIGN methodology; due to a lack of high-quality evidence these recommendations were formulated using the SIGN guidelines, which is acknowledged to be less robust than the GRADE approach. The correct diagnosis of PFS ensures the avoidance of a misdiagnosis of a primary peanut or tree nut allergy or confusion with another plant food allergy to non-specific lipid transfer proteins. The characteristic foods involved, and rapid-onset oropharyngeal symptoms, mean PFS can often be diagnosed from the clinical history alone. However, reactions involving tree nuts, peanuts and soya milk or severe/atypical reactions to fruits and vegetables may require additional diagnostic tests. Management is through the exclusion of known trigger foods, which may appear to be simple, but is highly problematic if coupled with a pre-existing food allergy or for individuals following a vegetarian/vegan diet. Immunotherapy to pollens is not an effective treatment for PFS, and although oral or sublingual immunotherapy to foods seems more promising, large, controlled studies are needed. The typically mild symptoms of PFS can lead to an erroneous perception that this condition is always easily managed, but severe reactions can occur, and anxiety about the onset of symptoms to new foods can have a profound effect on quality of life.


Assuntos
Hipersensibilidade Alimentar , Rinite Alérgica Sazonal , Adulto , Alérgenos , Arachis , Criança , Hipersensibilidade Alimentar/diagnóstico , Hipersensibilidade Alimentar/terapia , Frutas , Humanos , Pólen , Qualidade de Vida , Rinite Alérgica Sazonal/diagnóstico , Rinite Alérgica Sazonal/terapia , Testes Cutâneos , Síndrome , Reino Unido/epidemiologia
2.
Nanomedicine ; 39: 102464, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34583057

RESUMO

Mesenchymal stem cell therapy after stroke is a promising option investigated in animal models and clinical trials. The intravenous route is commonly used in clinical settings guaranteeing an adequate safety profile although low yields of engraftment. In this report, rats subjected to ischemic stroke were injected with adipose-derived stem cells (ADSCs) labeled with superparamagnetic iron oxide nanoparticles (SPIONs) applying an external magnetic field in the skull to retain the cells. Although most published studies demonstrate viability of ADSCs, only a few have used ultrastructural techniques. In our study, the application of a local magnetic force resulted in a tendency for higher yields of SPION-ADSCs targeting the brain. However, grafted cells displayed morphological signs of death, one day after administration, and correlative microscopy showed active microglia and astrocytes associated in the process of scavenging. Thus, we conclude that, although successfully targeted within the brain, SPION-ADSCs viability was rapidly compromised.


Assuntos
Nanopartículas de Magnetita , Acidente Vascular Cerebral , Adipócitos , Animais , Encéfalo , Campos Magnéticos , Imageamento por Ressonância Magnética/métodos , Nanopartículas de Magnetita/química , Ratos , Células-Tronco , Acidente Vascular Cerebral/terapia
3.
Rev Esp Enferm Dig ; 114(4): 234-235, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-34844414

RESUMO

We report the case of a 69-year-old male with a relevant alcohol consumption and a history of prostate cancer who underwent screening upper gastrointestinal endoscopy and colonoscopy. The upper gastrointestinal endoscopy revealed an ulcerated mass in the middle esophagus occupying half the circumference. Histologic examination was compatible with a squamous cell carcinoma. Staging with endoscopic ultrasound and computed tomography of the neck, chest and abdomen was consistent with a T3N1M0.


Assuntos
Carcinoma de Células Escamosas , Neoplasias Esofágicas , Idoso , Carcinoma de Células Escamosas/patologia , Endoscopia Gastrointestinal , Endossonografia , Neoplasias Esofágicas/diagnóstico por imagem , Neoplasias Esofágicas/patologia , Humanos , Masculino
4.
Chemistry ; 27(52): 13242-13248, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34268813

RESUMO

To design molecular spin qubits with enhanced quantum coherence, a control of the coupling between the local vibrations and the spin states is crucial, which could be realized in principle by engineering molecular structures via coordination chemistry. To this end, understanding the underlying structural factors that govern the spin relaxation is a central topic. Here, we report the investigation of the spin dynamics in a series of chemically designed europium(II)-based endohedral metallofullerenes (EMFs). By introducing a unique structural difference, i. e. metal-cage binding site, while keeping other molecular parameters constant between different complexes, these manifest the key role of the three low-energy metal-displacing vibrations in mediating the spin-lattice relaxation times (T1 ). The temperature dependence of T1 can thus be normalized by the frequencies of these low energy vibrations to show an unprecedentedly universal behavior for EMFs in frozen CS2 solution. Our theoretical analysis indicates that this structural difference determines not only the vibrational rigidity but also spin-vibration coupling in these EMF-based qubit candidates.

5.
Inorg Chem ; 60(12): 8575-8580, 2021 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-34096277

RESUMO

Embedding coherent spin motifs in reproducible molecular building blocks is a promising pathway for the realization of quantum technologies. Three-dimensional (3D) MOFs are a versatile platform for the rational design of extended structures employing coordination chemistry. Here, we report the synthesis and characterization of a gadolinium(III)-based MOF, [Gd(bipyNO)4](TfO)3·xMeOH (bipyNO = bipyridine,N,N'-dioxide; TfO = triflate; and MeOH = methanol) (quMOF-1), which presents a unique coordination geometry that leads to a tiny magnetic anisotropy (in terms of D, an equivalent zero-field splitting would be achieved by D = 0.006 cm-1) even compared with regular Gd(III) complexes. Pulsed electron paramagnetic resonance experiments on its magnetically diluted samples confirm the preservation of quantum coherence of single Gd(III) qubit units in this 3D extended molecular architecture (T2 = 612 ns and T1 = 66 µs at 3.5 K), which allows for the detection of Rabi oscillations at 40 K.

6.
Sensors (Basel) ; 21(9)2021 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-34068507

RESUMO

We reported measurement results relating to non-invasive glucose sensing using a novel multiwavelength approach that combines radio frequency and near infrared signals in transmission through aqueous glucose-loaded solutions. Data were collected simultaneously in the 37-39 GHz and 900-1800 nm electromagnetic bands. We successfully detected changes in the glucose solutions with varying glucose concentrations between 80 and 5000 mg/dl. The measurements showed for the first time that, compared to single modality systems, greater accuracy on glucose level prediction can be achieved when combining transmission data from these distinct electromagnetic bands, boosted by machine learning algorithms.


Assuntos
Fenômenos Eletromagnéticos , Água , Algoritmos , Glucose
7.
Sensors (Basel) ; 19(24)2019 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-31842266

RESUMO

We present an approach to enhance microwave brain imaging with an innovative metamaterial (MM) planar design based on a cross-shaped split-ring resonator (SRR-CS). The proposed metasurface is incorporated in different setups, and its interaction with EM waves is studied both experimentally and by using CST Microwave Studio® and is compared to a "no MM" case scenario. We show that the MM can enhance the penetration of the transmitted signals into the human head when placed in contact with skin tissue, acting as an impedance-matching layer. In addition, we show that the MM can improve the transceivers' ability to detect useful "weak" signals when incorporated in a headband scanner for brain imaging by increasing the signal difference from a blood-like dielectric target introduced into the brain volume. Our results suggest that the proposed MM film can be a powerful hardware advance towards the development of scanners for brain haemorrhage detection and monitoring.


Assuntos
Encéfalo/diagnóstico por imagem , Micro-Ondas , Neuroimagem/métodos , Encéfalo/fisiologia , Simulação por Computador , Impedância Elétrica , Estudos de Viabilidade , Humanos
8.
Strahlenther Onkol ; 194(1): 9-16, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28656373

RESUMO

INTRODUCTION: Although salvage radiotherapy (SRT) for PSA recurrence after radical prostatectomy provides better oncological outcomes when delivered early, in the absence of detectable disease many patients are treated for macroscopic locally recurrent tumors. Due to limited data from prospective studies, we hypothesized an important variability in the SRT management of these patients. Our aim was to investigate current practice patterns of SRT for local macroscopic recurrence after radical prostatectomy. MATERIAL AND METHODS: A total of 14 Swiss radiation oncology centers were asked to complete a survey on treatment specifications for macroscopic locally recurrent disease including information on pretherapeutic diagnostic procedures, dose prescription, radiation delivery techniques and androgen deprivation therapy (ADT). Treatment recommendations on ADT were analyzed using the objective consensus methodology. RESULTS: The majority of centers recommended pretreatment magnetic resonance imaging (MRI) of the pelvis and choline positron emission tomography (PET). The median prescribed dose to the prostate bed was 66 Gy (range 65-72 Gy) with a boost to the macroscopic lesion used by 79% of the centers with a median total dose of 72 Gy (range 70-80 Gy). Intensity-modulated rotational techniques were used by all centers and daily cone beam computed tomography (CT) was recommended by 43%. The use of concomitant ADT for any macroscopic recurrence was recommended by 43% of the centers while the remaining centers recommended it only for high-risk disease, which was not consistently defined. CONCLUSION: We observed a high variability of treatment paradigms when SRT is indicated for macroscopic local recurrences after prostatectomy. These data reflect the need for more standardized approaches and ultimately further research in this field.


Assuntos
Recidiva Local de Neoplasia/radioterapia , Complicações Pós-Operatórias/radioterapia , Padrões de Prática Médica , Prostatectomia , Neoplasias da Próstata/radioterapia , Humanos , Imageamento por Ressonância Magnética , Masculino , Recidiva Local de Neoplasia/patologia , Recidiva Local de Neoplasia/cirurgia , Tomografia por Emissão de Pósitrons , Complicações Pós-Operatórias/cirurgia , Neoplasias da Próstata/patologia , Neoplasias da Próstata/cirurgia , Dosagem Radioterapêutica , Terapia de Salvação , Suíça
9.
Langmuir ; 31(19): 5311-8, 2015 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-25919007

RESUMO

Self-assembled monolayers (SAMs) are nowadays broadly used as surface protectors or modifiers and play a key role in many technological applications. This has motivated the study of their formation in all kind of materials; however, and despite the current interest in molecular spintronics, the study of SAMs on ferromagnetic surfaces remains almost unexplored. In this paper, we report for the first time a methodology for the formation of SAMs of n-alkylphosphonic acids on permalloy in ambient conditions. The formed monolayers have been fully characterized by means of contact angle measurements, atomic force microscopy, X-ray photoelectron spectroscopy, matrix assisted laser desorption ionization time-of-flight mass spectrometry, infrared reflection absorption spectroscopy, and X-ray reflectometry. Additionally, the magnetic stability of the modified permalloy after the solution process required for the SAM formation has been confirmed by magneto-optical Kerr effect magnetometry. Moreover, by means of microcontact printing lithography, very accurate SAM patterns have been transferred onto permalloy surfaces and used as resist mask in a chemical etching process giving rise to submicrometric permalloy surface patterns with potential interest in nanomagnetism, spintronics, and storage technologies.

10.
Anal Bioanal Chem ; 406(8): 2211-5, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24105458

RESUMO

This work demonstrates the application of silica supported Fe3O4 nanoparticles as sorbent phase for magnetic solid-phase extraction (MSPE) and magnetic on-line in-tube solid-phase microextraction (Magnetic-IT-SPME) combined with capillary liquid chromatography-diode array detection (CapLC-DAD) to determine organophosphorous compounds (OPs) at trace level. In MSPE, magnetism is used as separation tool while in Magnetic-IT-SPME, the application of an external magnetic field gave rise to a significant improvement of the adsorption of OPs on the sorbent phase. Extraction efficiency, analysis time, reproducibility and sensitivity have been compared. This work showed that Magnetic-IT-SPME can be extended to OPs with successful results in terms of simplicity, speed, extraction efficiency and limit of detection. Finally, wastewater samples were analysed to determine OPs at nanograms per litre.


Assuntos
Compostos Organofosforados/química , Dióxido de Silício/química , Extração em Fase Sólida/métodos , Microextração em Fase Sólida/métodos , Poluentes Químicos da Água/química , Nanopartículas de Magnetita , Compostos Organofosforados/isolamento & purificação , Extração em Fase Sólida/instrumentação , Microextração em Fase Sólida/instrumentação , Águas Residuárias/química , Poluentes Químicos da Água/isolamento & purificação
11.
J Pathol Inform ; 14: 100180, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36687527

RESUMO

Introduction: The transition to digital pathology has been carried out by several laboratories across the globe, with some cases described in Portugal. In this article, we describe the transition to digital pathology in a high-volume private laboratory, considering the main challenges and opportunities. Material and methods: Our process started in 2020, with laboratory workflow adaptation and we are currently using a high-capacity scanner (Aperio GT450DX) to digitize slides at 20×. The visualization system, Aperio eSlide Manager WebViewer, is integrated into the Laboratory System. The validation process followed the Royal College of Pathologists Guidelines. Results: Regarding validation, the first phase detected an error rate of 6.8%, mostly due to digitization errors. Phase optimization and collaboration with technical services led to improvements in this process. In the second validation phase, most of the slides had the desired quality for evaluation, with only an error rate of 0.6%, corrected with a new scan. The interpathologist correlation had a total agreement rate of 96.87% and 3.13% partial agreement. Conclusion: The implementation and validation of digital pathology was a success, being ready for prime time. The total integration of all laboratory systems and the acquisition of new equipment will maximize their use, especially with the application of artificial intelligence algorithms.

12.
Anal Chem ; 84(16): 7233-40, 2012 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-22861152

RESUMO

We report a new in-tube solid phase microextraction approach named magnetic in-tube solid phase microextraction, magnetic-IT-SPME. Magnetic-IT-SPME has been developed, taking advantage of magnetic microfluidic principles with the aim to improve extraction efficiency of IT-SPME systems. First, a magnetic hybrid material formed by Fe(3)O(4) nanoparticles supported on SiO(2) was synthesized and immobilized in the surface of a bared fused silica capillary column to obtain a magnetic adsorbent extraction phase. The capillary column was placed inside a magnetic coil that allowed the application of a variable magnetic field. Acetylsalicylic acid, acetaminophen, atenolol, diclofenac, and ibuprofen were tested as target analytes. The application of a controlled magnetic field resulted in quantitative extraction efficiencies of the target analytes between 70 and 100%. These results demonstrated that magnetic forces solve the low extraction efficiency (10-30%) of IT-SPME systems, which is one of their main drawbacks.

13.
Adv Mater ; 34(49): e2206688, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36177716

RESUMO

Recent theory and experiments have showcased how to harness quantum mechanics to assemble heat/information engines with efficiencies that surpass the classical Carnot limit. So far, this has required atomic engines that are driven by cumbersome external electromagnetic sources. Here, using molecular spintronics, an implementation that is both electronic and autonomous is proposed. The spintronic quantum engine heuristically deploys several known quantum assets by having a chain of spin qubits formed by the paramagnetic Co center of phthalocyanine (Pc) molecules electronically interact with electron-spin-selecting Fe/C60 interfaces. Density functional calculations reveal that transport fluctuations across the interface can stabilize spin coherence on the Co paramagnetic centers, which host spin flip processes. Across vertical molecular nanodevices, enduring dc current generation, output power above room temperature, two quantum thermodynamical signatures of the engine's processes, and a record 89% spin polarization of current across the Fe/C60 interface are measured. It is crucially this electron spin selection that forces, through demonic feedback and control, charge current to flow against the built-in potential barrier. Further research into spintronic quantum engines, insight into the quantum information processes within spintronic technologies, and retooling the spintronic-based information technology chain, can help accelerate the transition to clean energy.

14.
Sci Rep ; 10(1): 10042, 2020 06 22.
Artigo em Inglês | MEDLINE | ID: mdl-32572087

RESUMO

We present a radio-frequency-activated switching system that can automatically detune a metamaterial resonator to enhance magnetic resonance imaging (MRI) performance. Local sensitivity-enhancing metamaterials typically consist of resonant components, which means that the transmitted radio frequency field is spatially inhomogeneous. The switching system shows for the first time that a metamaterial resonator can be detuned during transmission and tuned during reception using a digital circuit. This allows a resonating system to maintain homogeneous transmit field while maintaining an increased receive sensitivity. As a result, sensitivity can be enhanced without changing the system-provided specific absorption rate (SAR) models. The developed digital circuit consists of inductors sensitive to the transmit radio-frequency pulses, along with diodes acting as switches to control the resonance frequency of the resonator. We first test the automatic resonator detuning on-the-bench, and subsequently evaluate it in a 1.5 T MRI scanner using tissue-mimicking phantoms. The scan results demonstrate that the switching mechanism automatically detunes the resonator in transmit mode, while retaining its sensitivity-enhancing properties (tuned to the Larmor frequency) in receive mode. Since it does not require any connection to the MRI console, the switching system can have broad applications and could be adapted for use with other types of MRI scanners and field-enhancing resonators.

15.
Cerebrovasc Dis ; 27 Suppl 1: 104-10, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19342839

RESUMO

BACKGROUND: Sleep-disordered breathing (SDB) is a disease of increasing importance and it is frequent in stroke patients. SDB is being recognized as an independent risk factor for several clinical consequences, including cardiovascular and cerebrovascular disease. METHODS: The present review summarizes the current evidence for an independent association between SDB and stroke, defining SDB subgroups, mechanisms, confounding factors and other epidemiological aspects. We analyze stroke outcome and prognosis in SDB patients. A search for recent data on this issue was made in several population-based studies and reference lists of articles. RESULTS: Many recent studies have shown an association between SDB and stroke. Moreover, there is a high prevalence of sleep apnea in patients with stroke. The pathogenesis of stroke in obstructive sleep apnea syndrome is not completely understood and likely to be multifactorial. Several mechanisms like hemodynamic disturbances and inflammatory or endothelial dysfunction could be involved. The presence of SDB in stroke patients may lead to a poor outcome and recurrence. Noninvasive treatments such as continuous positive airway pressure may decrease the risk of stroke in terms of secondary, and possibly, primary prevention. CONCLUSIONS: SDB is associated with cerebrovascular morbidity and an unfavorable clinical course. The presence of SDB should be systematically screened in patients with acute stroke. Further studies are needed to determine whether continuous positive airway pressure treatment ameliorates stroke outcome and prognosis.


Assuntos
Síndromes da Apneia do Sono/complicações , Acidente Vascular Cerebral/etiologia , Pressão Positiva Contínua nas Vias Aéreas , Medicina Baseada em Evidências , Humanos , Radiografia , Recidiva , Medição de Risco , Fatores de Risco , Síndromes da Apneia do Sono/diagnóstico por imagem , Síndromes da Apneia do Sono/epidemiologia , Síndromes da Apneia do Sono/terapia , Acidente Vascular Cerebral/diagnóstico por imagem , Acidente Vascular Cerebral/epidemiologia , Acidente Vascular Cerebral/prevenção & controle , Resultado do Tratamento
16.
Acta Dermatovenerol Croat ; 27(1): 40-41, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31032791

RESUMO

Dear Editor, Angiolymphoid hyperplasia with eosinophilia (ALHE) is a rare, locally proliferating disorder that affects predominantly the head and neck region (1,2). There seems to be a higher incidence in middle-aged Caucasian women (2,3). A 28-year-old female patient with no relevant personal or family medical history and only taking an oral contraceptive, presented to our department with multiple, well delimited, infracentimetric erythematous papules with a smooth surface on the left frontal, temporal, and preauricular regions (Figure 1). The lesions had appeared 7 months earlier, with progressive growth in number and dimensions since. The patient reported pruritus and denied previous trauma, topical application of any sort, insect bite at these locations, and any other accompanying symptoms. A thorough physical examination revealed no additional abnormalities. An excisional biopsy of one of the left temporal papules revealed a prominent lymphoid component, with a dense multinodular infiltrate in the superficial and deep dermis, with reactive germinative centers of considerable dimensions (Figure 2). Large and atypical lymphocytes were confined to the germinative centers, with reactive characteristics. Lymphocytes surrounding the germinative centers were predominantly small, accompanied by a significant number of scattered eosinophils. CD3 and CD20 immunohistochemical staining revealed B-cells predominantly in the nodular areas corresponding to the germinative centers, while T-cells displayed a diffuse peripheral distribution. There was severe neovascularization, with thick-walled vascular channels lined by enlarged plump endothelial cells with an "epithelioid" appearance. These findings supported the diagnosis of angiolymphoid hyperplasia with eosinophilia (ALHE). Laboratory workup did not show any abnormalities, including eosinophilia or elevation of immunoglobulin E levels. Due to pruritus and aesthetic concerns, surgical excision of the larger and most symptomatic papules was performed. The patient was assured of the benign nature of the disease and informed about the possible development of new lesions. Kept under clinical surveillance, the patient remained free of new lesions at 6-month follow-up. ALHE generally presents as solitary or multiple erythematous or hyperpigmented dome-shaped papulonodules. Lesions can be pruritic or painful and do not tend to resolve spontaneously (4). The pathogenesis of ALHE remains controversial, although some theories have been suggested. The most widely accepted hypothesis is that it is an angioproliferative process, accompanied by an inflammatory infiltrate, reactive to several stimuli (3). Some authors believe it is an allergic reaction, but no specific sole agent has been identified (5). Others claim ALHE may represent a T-cell lymphoproliferative disorder of benign or low-grade malignant nature (6). Some recent studies suggest that ALHE pathogenesis may be related to a vascular malformation secondary to a subcutaneous arteriovenous shunt (1-3). Histologically there are both vascular and inflammatory components, with an abnormal vascular proliferation and diffuse lymphocytic infiltrates with eosinophils. The vascular component is formed by capillaries clustered around arterial or venous vessels, dilated and atypical, with a protruded endothelium (3). The main differential diagnosis of ALHE is Kimura's disease, and there has been some discussion regarding the relationship between these two entities due to their clinical and histopathological similarities. However, most studies currently agree that they are distinct diseases. The differential diagnosis also includes angiosarcoma, particularly the epithelioid variant, epithelioid hemangioendothelioma, Kaposi sarcoma, pyogenic granuloma, and cutaneous metastasis (3). ALHE usually requires treatment as spontaneous regression, although reported in the literature, is rare (1,3). Many options have been suggested, with variable levels of success, but there is no definitive treatment for this condition (2). Surgical excision is the preferred choice, but recurrence may happen if the excision is incomplete (1). Mohs micrographic surgery with excision of abnormal vessels at the base of the lesion may be more effective in reducing recurrences (4). Other treatments reported include laser therapy (pulsed dye, CO2, copper vapor), systemic or intralesional corticosteroid injection, cryotherapy, imiquimod, tacrolimus, isotretinoin, radiotherapy, interferon alfa 2a, anti-interleukin-5 antibody, photodynamic therapy, and methotrexate (1). In the present case the diagnosis of ALHE was established through the conjunction of clinical and histological findings. Although a rare entity, its predominantly facial involvement in young adults and the absence of a satisfactory treatment can produce a significant impact that can include the quality of life of the patients.


Assuntos
Hiperplasia Angiolinfoide com Eosinofilia/diagnóstico , Hiperplasia Angiolinfoide com Eosinofilia/terapia , Dermatoses Faciais/diagnóstico , Dermatoses Faciais/terapia , Adulto , Feminino , Humanos
17.
Annu Int Conf IEEE Eng Med Biol Soc ; 2019: 6810-6813, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31947404

RESUMO

Magnetic resonance imaging (MRI) is a widely used clinical tool for medical diagnosis and therapy. Several research studies focus on passively improving MRI sensitivity using high dielectric constant (HDC) materials and metamaterials. In this work, we investigate a new metasurface resonator which can enhance local transmit and receive efficiency in 1.5T MRI. The metasurface has been realized with an array of non-magnetic rods embedded in two blocks of a BaTiO3 aqueous mixture. BaTiO3 when mixed with water exhibits high dielectric permittivity values in the 40-200 MHz range, allowing the design of a compact and safe device for practical use in an MRI scanner. Simulation results show 50% enhancement of the magnetic field in the region-of-interest. The resonance frequency of the metasurface is also validated experimentally with a small loop antenna and a vector network analyzer (VNA) in a laboratory-controlled environment.


Assuntos
Imageamento por Ressonância Magnética , Compostos de Bário , Desenho de Equipamento , Campos Magnéticos , Imagens de Fantasmas , Titânio , Água
18.
Adv Mater ; 31(28): e1900189, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31081262

RESUMO

The rapid rise in energy demand in the past years has prompted a search for low-cost alternatives for energy storage, supercapacitors being one of the most important devices. It is shown that a dramatic enhancement (≈1100%, from 155 to 1850 F g-1 ) of the specific capacitance of a hybrid stimuli-responsive FeNi3 -graphene electrode material can be achieved when the charge/discharge cycling is performed in the presence of an applied magnetic field of 4000 G. This result is related to an unprecedented magnetic-field-induced metal segregation of the FeNi3 nanoparticles during the cycling, which results in the appearance of small Ni clusters (<5 nm) and, consequently, in an increase in pseudocapacitive sites. The results open the door to a systematic improvement of the capacitance values of hybrid supercapacitors, while moving the research in this area towards the development of magnetically addressable energy-storage devices.

19.
Annu Int Conf IEEE Eng Med Biol Soc ; 2019: 1183-1186, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31946105

RESUMO

The investigation of variations in dielectric properties of blood based on its biochemical profile is important for determining the feasibility of developing electromagnetic non-invasive sensing systems for monitoring the levels of various metabolites in blood. In this paper, the real and imaginary parts of dielectric permittivity are measured as a function of lactate concentration in the 30-60 GHz frequency range using two different measurement techniques. The blood samples are collected from a healthy subject undergoing three different exercise modes and the dielectric properties are measured with an open-ended coaxial probe technique and a custom-made millimeter wave transmission system. Good correlation is observed in measurements from the two methods, suggesting that an increase in lactate concentration lowers the imaginary part of permittivity and thus causing higher attenuation.


Assuntos
Fenômenos Eletromagnéticos , Lactatos , Radiação , Humanos , Lactatos/sangue
20.
Annu Int Conf IEEE Eng Med Biol Soc ; 2019: 6032-6035, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31947221

RESUMO

We present proof of concept experiment of a sensing method to detect skin hydration using a low-cost bio-impedance sensor. The sensing system is validated by testing its current output over frequencies between 1 kHz and 50 kHz and comparing measured values of impedance. A series of experiments with salt-water mixtures as well as a gelatin-based phantom were carried out to test the sensor's ability to detect small changes in impedance due to changes in water content. We also compared impedance measurements from the phantom to human skin to confirm that the manufactured phantoms can mimic skin properties successfully. Our experimental results show that the sensor can detect small changes in salt concentration and can capture the correlation between the impedance and skin hydration in a reliable manner.


Assuntos
Pele , Impedância Elétrica , Estudos de Viabilidade , Humanos , Imagens de Fantasmas
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