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1.
Sensors (Basel) ; 22(6)2022 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-35336548

RESUMO

Recognizing human emotions by machines is a complex task. Deep learning models attempt to automate this process by rendering machines to exhibit learning capabilities. However, identifying human emotions from speech with good performance is still challenging. With the advent of deep learning algorithms, this problem has been addressed recently. However, most research work in the past focused on feature extraction as only one method for training. In this research, we have explored two different methods of extracting features to address effective speech emotion recognition. Initially, two-way feature extraction is proposed by utilizing super convergence to extract two sets of potential features from the speech data. For the first set of features, principal component analysis (PCA) is applied to obtain the first feature set. Thereafter, a deep neural network (DNN) with dense and dropout layers is implemented. In the second approach, mel-spectrogram images are extracted from audio files, and the 2D images are given as input to the pre-trained VGG-16 model. Extensive experiments and an in-depth comparative analysis over both the feature extraction methods with multiple algorithms and over two datasets are performed in this work. The RAVDESS dataset provided significantly better accuracy than using numeric features on a DNN.


Assuntos
Aprendizado Profundo , Fala , Algoritmos , Emoções , Humanos , Redes Neurais de Computação
2.
Artif Organs ; 44(8): E369-E381, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32219877

RESUMO

Human kidneys tend to be affected adversely and fail to function more often than any other organ in the body because of diet, heredity, and lifestyle of a person. Dialysis is the technique presently in use for replacing the failed kidney function but it is packed with painfulness, bulkiness, and is costly also. There is a growing need for development of an artificial kidney that eradicates the problems associated with dialysis. This article proposes a structure that mimics the most important aspect of the human kidney: the size-dependent reabsorption of endothelial cells in the proximal convoluted tubule (PCT). The proposed structure consists of transporting channels connecting blood tubules surrounded on both sides of a main tubule. Geometries of the channels are analyzed for optimum flow by varying angles with respect to the main tubule. The analytical formulae have been developed by considering proper boundary conditions governing the flow in the structure, which makes the model as robust, concise, and realistic as the actual PCT. The mathematical model is validated against the benchmark FEM tool COMSOL Multiphysics and the results seem to be satisfactory. This article concludes, that slant channels possess a considerably higher average flow velocity of 5.39 × 10-5  m/s (≈52% reabsorption rate) than straight channels with 4.77 × 10-5  m/s (≈46% reabsorption rate) which is closer to the actual PCT reabsorption rate of 60%. The proposed model is first of its kind in nature among the reported works which creates and exhibits simulation environment of PCT reabsorption function supported by mathematical formulation and also can be useful to study and develop artificial kidney in near future.


Assuntos
Rins Artificiais , Humanos , Túbulos Renais Proximais/fisiologia , Microfluídica , Modelos Anatômicos , Modelos Biológicos , Desenho de Prótese
3.
Urol Int ; 103(2): 218-222, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30970368

RESUMO

OBJECTIVES: To highlight the transvaginal route as an excellent approach for repair of a simple trigonal, supra-trigonal vesico-vaginal and urethrovaginal fistulae without compromising on the successful patient outcomes. We also determine factors affecting outcomes in such patients. MATERIALS AND METHODS: A retrospective analysis was carried out on 58 patients with simple trigonal, supra trigonal and urethrovaginal fistula who underwent transvaginal repair in the last 10 years. Simple fistulas were defined as fistula less than 3 cm in size or recurrent fistulae less than 1.5-2 cm in size and located either supra-trigonally (above the bar of mercier) or sub-trigonally (below the bar of mercier) as determined by cystoscopy. RESULTS: Obstetric cause, due to obstructed labour, was the most common cause of fistula formation (68.96%), while remaining (29.31%) were attributed to hysterectomy. Primary fistulae were found in 68.9% of patients and recurrent fiistulae in 31.1% patients. The mean age of patients was 33.4 years. Average fistula size was 1.5 cm. The success rate of primary operation was 84.12% (50/58). On using a multivariate regression model, the underlying aetiology (OR 2.2), fistula location (OR 2.5) and history of previous repair (OR 2.4) were found to be significant factors affecting outcome. CONCLUSION: The transvaginal approach is less invasive and achieves comparable success rates as compared to other methods of vesico-vaginal fistula repair. This surgery with Foley catheter has a high success rate with reduced morbidity. We postulate that vaginal approach should be preferred over abdominal approach for repair of all vaginally accessible vesico vaginal fistulae, both of obstetrical and gynaecological origin.


Assuntos
Doenças Uretrais/cirurgia , Fístula Urinária/cirurgia , Fístula Vaginal/cirurgia , Fístula Vesicovaginal/cirurgia , Adulto , Feminino , Procedimentos Cirúrgicos em Ginecologia/métodos , Humanos , Estudos Retrospectivos , Fatores de Tempo , Resultado do Tratamento , Procedimentos Cirúrgicos Urológicos/métodos , Vagina
4.
Vasc Med ; 22(5): 426-431, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28990495

RESUMO

The formation of a fistula between the internal mammary artery and the pulmonary vasculature (IMA-to-PV) is a rare anomaly. The etiology can be congenital; however, most recent cases have been associated with coronary artery bypass grafting, trauma, inflammatory conditions, chronic infections, or neoplasia. The knowledge base on the formation of these fistulas is derived primarily from case reports. To our knowledge, no systematic reviews or guidelines are available that provide information on how to manage these cases, and the treatment of an IMA-to-PV fistula is controversial. To our knowledge, this report is the first to review 80 cases of IMA-to-PV fistulas reported in the literature. We describe the etiologies, clinical presentation, and management of these fistulas.


Assuntos
Fístula Artério-Arterial/etiologia , Fístula Arteriovenosa/etiologia , Artéria Torácica Interna , Artéria Pulmonar , Veias Pulmonares , Lesões do Sistema Vascular/etiologia , Adulto , Fístula Artério-Arterial/diagnóstico por imagem , Fístula Artério-Arterial/terapia , Fístula Arteriovenosa/diagnóstico por imagem , Fístula Arteriovenosa/terapia , Feminino , Humanos , Doença Iatrogênica , Masculino , Artéria Torácica Interna/anormalidades , Artéria Torácica Interna/diagnóstico por imagem , Artéria Torácica Interna/lesões , Pessoa de Meia-Idade , Artéria Pulmonar/anormalidades , Artéria Pulmonar/diagnóstico por imagem , Artéria Pulmonar/lesões , Veias Pulmonares/anormalidades , Veias Pulmonares/diagnóstico por imagem , Veias Pulmonares/lesões , Fatores de Risco , Resultado do Tratamento , Lesões do Sistema Vascular/diagnóstico por imagem , Lesões do Sistema Vascular/terapia
5.
Echocardiography ; 34(6): 928-933, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28401711

RESUMO

Atherosclerotic subclavian artery disease is detected in about 5% of patients referred for coronary artery bypass (CABG) surgery. The internal mammary artery, a branch of the subclavian artery, is the most frequently utilized graft to restore coronary circulation because of its longevity. Stenosis or occlusion of the subclavian artery can cause retrograde blood flow in the ipsilateral internal mammary artery, known as "steal," compromising coronary circulation supplied by the graft. Steal may be asymptomatic or may result in symptoms of myocardial ischemia. Symptomatic subclavian artery stenosis post bypass is referred to as coronary subclavian steal syndrome post-CABG. The incidence is not well defined, and the benefits of screening patients referred for CABG are not known. Despite the various modalities available to detect subclavian artery stenosis, current guidelines fail to provide guidance about screening high-risk patients for this entity. Detection of subclavian artery disease prior to CABG can reduce complications posed by post-mammary artery graft cardiac ischemia. This review discusses the utility of preoperative subclavian artery screening prior to CABG.


Assuntos
Ponte de Artéria Coronária , Cuidados Pré-Operatórios/métodos , Síndrome do Roubo Subclávio/diagnóstico por imagem , Ultrassonografia/métodos , Encéfalo/irrigação sanguínea , Encéfalo/diagnóstico por imagem , Humanos
6.
ScientificWorldJournal ; 2015: 704049, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25821856

RESUMO

Paxos is a prominent theory of state-machine replication. Recent data intensive systems that implement state-machine replication generally require high throughput. Earlier versions of Paxos as few of them are classical Paxos, fast Paxos, and generalized Paxos have a major focus on fault tolerance and latency but lacking in terms of throughput and scalability. A major reason for this is the heavyweight leader. Through offloading the leader, we can further increase throughput of the system. Ring Paxos, Multiring Paxos, and S-Paxos are few prominent attempts in this direction for clustered data centers. In this paper, we are proposing HT-Paxos, a variant of Paxos that is the best suitable for any large clustered data center. HT-Paxos further offloads the leader very significantly and hence increases the throughput and scalability of the system, while at the same time, among high throughput state-machine replication protocols, it provides reasonably low latency and response time.

7.
Indian J Crit Care Med ; 18(4): 238-40, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24872654

RESUMO

A 77-year-old male patient presented with rhabdomyolysis. He developed progressive respiratory failure and acute respiratory distress syndrome during his hospital stay requiring mechanical ventilation. An electrocardiogram during mechanical ventilation showed findings suggestive of ST elevation myocardial infarction. Closer review showed dome and spike findings that have been likened to a "spiked helmet." This finding has been associated with significant mortality. We discuss this under-recognized finding and the potential contributing mechanisms.

8.
J Neurooncol ; 112(3): 413-20, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23417357

RESUMO

Pseudo-progression (PsP) refers to the paradoxical increase of contrast enhancement within 12 weeks of chemo-radiation therapy in gliomas attributable to treatment effects rather than early tumor progression (ETP). This study was performed to evaluate the utility of morphologic imaging features, diffusion tensor imaging (DTI) and radiation dosimetric analysis of magnetic resonance imaging (MRI) changes in differentiating PsP from ETP. Serial MRI examinations of 163 patients treated for high-grade glioma were reviewed. 46 patients showed a recurrent or progressive enhancing lesion within 12 weeks of radiotherapy. We used an in-house modified scoring system based on 20 different morphologic features (modified VASARI features) to assess the MRI studies. DTI analyses were performed in 24 patients. MRI changes were defined as recurrent volume (Vrec) and registered with pretreatment computed tomography dataset, and the actual dose received by the Vrec during treatment was calculated using dose-volume histograms. Bidimensional product of T2-FLAIR signal abnormality and enhancing component was larger in the ETP group. DTI metrics revealed no significant difference between the two groups. There was no statistically significant difference in the location of Vrec between PsP and ETP groups. Morphologic MRI features and DTI have a limited role in differentiating between PsP and ETP. The larger sizes of the T2-FLAIR signal abnormality and the enhancing component of the lesion favor ETP. There was no correlation between the pattern of MRI changes and radiation dose distribution between PsP and ETP groups.


Assuntos
Neoplasias Encefálicas/patologia , Neoplasias Encefálicas/terapia , Quimiorradioterapia/efeitos adversos , Glioblastoma/patologia , Glioblastoma/terapia , Antineoplásicos/administração & dosagem , Antineoplásicos/efeitos adversos , Dacarbazina/administração & dosagem , Dacarbazina/efeitos adversos , Dacarbazina/análogos & derivados , Imagem de Difusão por Ressonância Magnética , Progressão da Doença , Feminino , Humanos , Interpretação de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Radiometria , Radioterapia/efeitos adversos , Temozolomida
9.
Eur J Cancer ; 183: 95-97, 2023 04.
Artigo em Inglês | MEDLINE | ID: mdl-36812845

RESUMO

Clinical research is crucial for national cancer control plans. Prior to the Russian invasion on 24th Feb 2022 both Russia and Ukraine were significant contributors to global clinical trials and cancer research. In this short analysis we describe this and the impact that the conflict has had with wider consideration for the global cancer research ecosystems.


Assuntos
Ecossistema , Neoplasias , Humanos , Ucrânia/epidemiologia , Federação Russa/epidemiologia , Neoplasias/epidemiologia
10.
ACS Omega ; 8(39): 36521-36533, 2023 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-37810638

RESUMO

Carbon dots (CDs) are promising biocompatible fluorescent nanoparticles mainly used in bioimaging, drug delivery, sensing, therapeutics, and various other applications. The utilization of natural sources and green synthetic approaches is resulting in highly biocompatible and nontoxic nanoparticles. Herein, we report an unprecedented facile and green synthesis of highly luminescent carbon dots derived from camel milk (CM) for sensing manganese (Mn7+) ions and for identifying the anticancer potential and antiamyloid activity against α-synuclein amyloids. α-Synuclein amyloid formation due to protein misfolding (genetic and environmental factors) has gained significant attention due to its association with Parkinson's disease and other synucleinopathies. The as-synthesized CM-CDs possess an average hydrodynamic diameter ranging from 3 to 15 nm and also exhibit strong photoluminescence (PL) emission in the blue region. The CM-CDs possess good water dispersibility, stable fluorescence under different physical states, and outstanding photostability. Moreover, the CM-CDs are validated as an efficient sensor for the detection of Mn7+ ions in DI water and in metal ion-polluted tap water. In addition, the CM-CDs have demonstrated a very good quantum yield (QY) of 24.6% and a limit of detection (LOD) of 0.58 µM for Mn7+ ions with no incubation time. Consequently, the exceptional properties of CM-CDs make them highly suitable for a diverse array of biomedical applications.

11.
Clin J Am Soc Nephrol ; 18(3): 315-326, 2023 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-36787125

RESUMO

BACKGROUND: Up to 14% of patients in the United States undergoing cardiac catheterization each year experience AKI. Consistent use of risk minimization preventive strategies may improve outcomes. We hypothesized that team-based coaching in a Virtual Learning Collaborative (Collaborative) would reduce postprocedural AKI compared with Technical Assistance (Assistance), both with and without Automated Surveillance Reporting (Surveillance). METHODS: The IMPROVE AKI trial was a 2×2 factorial cluster-randomized trial across 20 Veterans Affairs medical centers (VAMCs). Participating VAMCs received Assistance, Assistance with Surveillance, Collaborative, or Collaborative with Surveillance for 18 months to implement AKI prevention strategies. The Assistance and Collaborative approaches promoted hydration and limited NPO and contrast dye dosing. We fit logistic regression models for AKI with site-level random effects accounting for the clustering of patients within medical centers with a prespecified interest in exploring differences across the four intervention arms. RESULTS: Among VAMCs' 4517 patients, 510 experienced AKI (235 AKI events among 1314 patients with preexisting CKD). AKI events in each intervention cluster were 110 (13%) in Assistance, 122 (11%) in Assistance with Surveillance, 190 (13%) in Collaborative, and 88 (8%) in Collaborative with Surveillance. Compared with sites receiving Assistance alone, case-mix-adjusted differences in AKI event proportions were -3% (95% confidence interval [CI], -4 to -3) for Assistance with Surveillance, -3% (95% CI, -3 to -2) for Collaborative, and -5% (95% CI, -6 to -5) for Collaborative with Surveillance. The Collaborative with Surveillance intervention cluster had a substantial 46% reduction in AKI compared with Assistance alone (adjusted odds ratio=0.54; 0.40-0.74). CONCLUSIONS: This implementation trial estimates that the combination of Collaborative with Surveillance reduced the odds of AKI by 46% at VAMCs and is suggestive of a reduction among patients with CKD. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: IMPROVE AKI Cluster-Randomized Trial (IMPROVE-AKI), NCT03556293.


Assuntos
Injúria Renal Aguda , Tutoria , Insuficiência Renal Crônica , Humanos , Estados Unidos , Meios de Contraste/efeitos adversos , United States Department of Veterans Affairs , Insuficiência Renal Crônica/induzido quimicamente , Injúria Renal Aguda/induzido quimicamente , Injúria Renal Aguda/prevenção & controle
12.
Acta Radiol ; 53(6): 682-8, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22761347

RESUMO

BACKGROUND: Idiopathic intracranial hypertension (IIH) is a clinical disorder of unknown etiology manifesting with increased intracranial pressure in the absence of hydrocephalus, an underlying mass lesion, and demonstrating normal cerebrospinal fluid composition. IIH may exhibit several non-specific imaging findings including: an empty sella, posterior globe flattening, tortuosity of the optic nerve, and optic nerve sheath distention. PURPOSE: To introduce widening of the foramen ovale as a new imaging marker for IIH. MATERIAL AND METHODS: IIH is a syndrome which may exhibit several previously described non-specific imaging findings including: an empty sella, posterior globe flattening, tortuosity of the optic nerve, and optic nerve sheath distention. We hypothesize that chronically elevated cerebrospinal fluid pressure can lead to osseous erosions and we propose widening of the foramen ovale as a new imaging marker for IIH. RESULTS: Average foramen ovale sizes were increased in patients with IIH compared to controls (30.03 ± 7.00 mm(2) vs. 24.21 ± 5.97 mm(2), P < 0.001). For a cut-off value of 30 mm(2), the sensitivity of FO area to detect IIH was 50%, with 81% specificity. Classic findings were significantly more common in patients with IIH compared to controls including: empty sella (65.9% vs. 0%), posterior globe flattening (65.9% vs. 4.5%), vertical tortuosity of the optic nerve (54.5% vs. 9.1%), and optic nerve sheath distention (52.3% vs. 11.4%, all P values < 0.001). CONCLUSION: Our study confirms the association of several classic imaging findings with IIH and supports widening of the foramen ovale as an additional imaging marker which may be incorporated into the evaluation of patients suspected to have this condition.


Assuntos
Forame Oval/diagnóstico por imagem , Forame Oval/patologia , Imageamento por Ressonância Magnética/métodos , Pseudotumor Cerebral/diagnóstico , Tomografia Computadorizada por Raios X/métodos , Adulto , Área Sob a Curva , Feminino , Humanos , Masculino , Variações Dependentes do Observador , Curva ROC , Reprodutibilidade dos Testes , Estudos Retrospectivos , Sensibilidade e Especificidade
13.
J Photochem Photobiol B ; 234: 112545, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-36049288

RESUMO

Clinical diagnostics for SARS-CoV-2 infection usually comprises the sampling of throat or nasopharyngeal swabs that are invasive and create patient discomfort. Hence, saliva is attempted as a sample of choice for the management of COVID-19 outbreaks that cripples the global healthcare system. Although limited by the risk of eliciting false-negative and positive results, tedious test procedures, requirement of specialized laboratories, and expensive reagents, nucleic acid-based tests remain the gold standard for COVID-19 diagnostics. However, genetic diversity of the virus due to rapid mutations limits the efficiency of nucleic acid-based tests. Herein, we have demonstrated the simplest screening modality based on label-free surface enhanced Raman scattering (LF-SERS) for scrutinizing the SARS-CoV-2-mediated molecular-level changes of the saliva samples among healthy, COVID-19 infected and COVID-19 recovered subjects. Moreover, our LF-SERS technique enabled to differentiate the three classes of corona virus spike protein derived from SARS-CoV-2, SARS-CoV and MERS-CoV. Raman spectral data was further decoded, segregated and effectively managed with the aid of machine learning algorithms. The classification models built upon biochemical signature-based discrimination method of the COVID-19 condition from the patient saliva ensured high accuracy, specificity, and sensitivity. The trained support vector machine (SVM) classifier achieved a prediction accuracy of 95% and F1-score of 94.73%, and 95.28% for healthy and COVID-19 infected patients respectively. The current approach not only differentiate SARS-CoV-2 infection with healthy controls but also predicted a distinct fingerprint for different stages of patient recovery. Employing portable hand-held Raman spectrophotometer as the instrument and saliva as the sample of choice will guarantee a rapid and non-invasive diagnostic strategy to warrant or assure patient comfort and large-scale population screening for SARS-CoV-2 infection and monitoring the recovery process.


Assuntos
COVID-19 , Ácidos Nucleicos , Inteligência Artificial , COVID-19/diagnóstico , Teste para COVID-19 , Atenção à Saúde , Humanos , SARS-CoV-2 , Saliva
14.
Cureus ; 13(12): e20535, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-35103122

RESUMO

We discuss the case of a 36-year-old male patient who presented with gait impairment. On examination, he had clinical findings of cervical myelopathy. The patient was evaluated with an MRI of the brain and spine, which revealed multiple spinal tumors, some causing significant canal stenosis. The spinal tumors involved the cervical, thoracic, and lumbar regions. There were both intramedullary and extramedullary tumors with an extraspinal extension. The patient's MRI brain also revealed bilateral vestibular schwannomas. His family history was negative. He subsequently underwent surgery for multiple spinal lesions followed by debulking of the right-sided vestibular schwannoma. The radiological findings of both intramedullary and extramedullary spinal tumors affecting the spinal cord and extensively involving the cervical, thoracic, and lumbar regions, and the requirement of spinal and cranial surgery concurrently make this a challenging neurosurgical case.

15.
Cureus ; 13(3): e14091, 2021 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-33927915

RESUMO

Regadenoson myocardial perfusion imaging (MPI) is a widely used screening study for patients with an intermediate pretest probability of coronary artery disease (CAD). Via selective agonism of the adenosine A2A receptor, regadenoson can induce coronary steal, revealing stenotic vessel territory through transient ischemia. Common side effects of this medication include chest pain, shortness of breath, nausea, vomiting, atrioventricular block, seizure, and allergic reactions. Here we present a case of severe shivering and chest tightness after the administration of regadenoson, along with a physiologic explanation and treatment.

16.
Cureus ; 13(6): e15659, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34277252

RESUMO

Penile strangulation is not commonly encountered in orthopedic practice. Quick decision and immediate removal of the metallic ring with readily available instruments is the key to a successful outcome. Jumbo cutter is a commonly available instrument. It can be used with ease without causing any thermal or soft tissue damage, giving satisfactory results.

17.
Elife ; 102021 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-33876727

RESUMO

To understand the spread of SARS-CoV2, in August and September 2020, the Council of Scientific and Industrial Research (India) conducted a serosurvey across its constituent laboratories and centers across India. Of 10,427 volunteers, 1058 (10.14%) tested positive for SARS-CoV2 anti-nucleocapsid (anti-NC) antibodies, 95% of which had surrogate neutralization activity. Three-fourth of these recalled no symptoms. Repeat serology tests at 3 (n = 607) and 6 (n = 175) months showed stable anti-NC antibodies but declining neutralization activity. Local seropositivity was higher in densely populated cities and was inversely correlated with a 30-day change in regional test positivity rates (TPRs). Regional seropositivity above 10% was associated with declining TPR. Personal factors associated with higher odds of seropositivity were high-exposure work (odds ratio, 95% confidence interval, p value: 2.23, 1.92-2.59, <0.0001), use of public transport (1.79, 1.43-2.24, <0.0001), not smoking (1.52, 1.16-1.99, 0.0257), non-vegetarian diet (1.67, 1.41-1.99, <0.0001), and B blood group (1.36, 1.15-1.61, 0.001).


Assuntos
Anticorpos Neutralizantes/sangue , Anticorpos Antivirais/sangue , Teste Sorológico para COVID-19 , COVID-19/epidemiologia , SARS-CoV-2/imunologia , Biomarcadores/sangue , COVID-19/diagnóstico , COVID-19/imunologia , COVID-19/virologia , Feminino , Interações Hospedeiro-Patógeno , Humanos , Imunidade Humoral , Índia/epidemiologia , Estudos Longitudinais , Masculino , Valor Preditivo dos Testes , Medição de Risco , Fatores de Risco , Estudos Soroepidemiológicos , Fatores de Tempo
18.
Nanotechnology ; 21(40): 405505, 2010 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-20829571

RESUMO

Here we show how the electromechanical properties of silicon nanowires (NWs) are modified when they are subjected to extreme mechanical deformations (buckling and buckling mode transitions), such as those appearing in flexible devices. Flexible devices are prone to frequent dynamic stress variations, especially buckling, while the small size of NWs could give them an advantage as ultra-sensitive electromechanical stress sensors embedded in such devices. We evaluated the NWs post-buckling behavior and the effects of buckling mode transition on their piezoresistive gauge factor (GF). Polycrystalline silicon NWs were embedded in SiO(2) microbridges to facilitate concurrent monitoring of their electrical resistance without problematic interference, while an external stylus performed controlled deformations of the microbridges. At points of instability, the abrupt change in the buckling configuration of the microbridge corresponded to a sharp resistance change in the embedded NWs, without altering the NWs' GF. These results also highlight the importance of strategically positioning the NW in the devices, since electrical monitoring of buckling mode transitions is feasible when the deformations impact a region where the NW is placed. The highly flexible NWs also exhibited unusually large fracture strength, sustaining tensile strains up to 5.6%; this will prove valuable in demanding flexible sensors.


Assuntos
Eletricidade , Fenômenos Mecânicos , Nanofios/química , Silício/química , Estresse Mecânico , Nanofios/ultraestrutura , Propriedades de Superfície
19.
Pediatr Radiol ; 40(12): 1958-61, 2010 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-20821201

RESUMO

We report on an 11-year-old girl suffering from a typical attack of hemiplegic migraine with characteristic abnormalities in perfusion MR and susceptibility-weighted MR imaging findings. The imaging abnormalities were resolved 48 h after the attack. Susceptibility-weighted MR imaging findings correlated well with the MR perfusion, thus it can be used along with conventional MRI for evaluation of children with complex migraine attacks. Susceptibility-weighted MR imaging might have a diagnostic role in assessing the vascular events in hemiplegic migraine.


Assuntos
Encéfalo/patologia , Hemiplegia/diagnóstico , Angiografia por Ressonância Magnética/métodos , Transtornos de Enxaqueca/diagnóstico , Transtornos de Enxaqueca/tratamento farmacológico , Acetazolamida/uso terapêutico , Anticonvulsivantes/uso terapêutico , Criança , Feminino , Hemiplegia/tratamento farmacológico , Hemiplegia/etiologia , Humanos , Transtornos de Enxaqueca/complicações , Resultado do Tratamento
20.
Biomicrofluidics ; 14(2): 024103, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32206158

RESUMO

Particle filtration and concentration have great significance in a multitude of applications. Physical filters are nearly indispensable in conventional separation processes. Similarly, microfabrication-based physical filters are gaining popularity as size-based particle sorters, separators, and prefiltration structures for microfluidics platforms. The work presented here introduces a linear combination of obstructions to provide size contrast-based particle separation. Polystyrene particles that are captured along the crossflow filters are packed in the direction of the dead-end filters. Separation of polydisperse suspension of 5 µm and 10 µm diameter polystyrene microspheres is attained with capture efficiency for larger particles as 95%. Blood suspension is used for biocharacterization of the device. A flow induced method is used to improve particle capture uniformity in a single microchannel and reduce microgap clogging to about 30%. This concept is extended to obtain semiquantification obtained by comparison of the initial particle concentration to captured-particle occupancy in a microfiltration channel.

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