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1.
Sensors (Basel) ; 19(20)2019 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-31640259

RESUMO

We address wideband direct coherent localization of a radio transmitter by a distributed antenna array in a multipath scenario with spatially-coherent line-of-sight (LoS) signal components. Such a signal scenario is realistic in small cells, especially indoors in the mmWave range. The system model considers collocated time and phase synchronized receiving front-ends with antennas distributed in 3D space at known locations connected to the front-ends via calibrated coaxial cables or analog radio frequency over fiber links. The signal model assumes spherical wavefronts. We propose two ML-type algorithms (for known and unknown transmitter waveforms) and a subspace-based SCM-MUSIC algorithm for wideband direct coherent position estimation. We demonstrate the performance of the methods by Monte Carlo simulations. The results show that even in multipath environments, it is possible to achieve localization accuracy that is much better (by two to three orders of magnitude) than the carrier wavelength. They also suggest that the methods that do not exploit knowledge of the waveform have mean-squared errors approaching the Cramér-Rao bound.

2.
Acta Obstet Gynecol Scand ; 98(9): 1207-1217, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31081113

RESUMO

The second Signal Processing and Monitoring in Labor workshop gathered researchers who utilize promising new research strategies and initiatives to tackle the challenges of intrapartum fetal monitoring. The workshop included a series of lectures and discussions focusing on: new algorithms and techniques for cardiotocogoraphy (CTG) and electrocardiogram acquisition and analyses; the results of a CTG evaluation challenge comparing state-of-the-art computerized methods and visual interpretation for the detection of arterial cord pH <7.05 at birth; the lack of consensus about the role of intrapartum acidemia in the etiology of fetal brain injury; the differences between methods for CTG analysis "mimicking" expert clinicians and those derived from "data-driven" analyses; a critical review of the results from two randomized controlled trials testing the former in clinical practice; and relevant insights from modern physiology-based studies. We concluded that the automated algorithms performed comparably to each other and to clinical assessment of the CTG. However, the sensitivity and specificity urgently need to be improved (both computerized and visual assessment). Data-driven CTG evaluation requires further work with large multicenter datasets based on well-defined labor outcomes. And before first tests in the clinic, there are important lessons to be learnt from clinical trials that tested automated algorithms mimicking expert CTG interpretation. In addition, transabdominal fetal electrocardiogram monitoring provides reliable CTG traces and variability estimates; and fetal electrocardiogram waveform analysis is subject to promising new research. There is a clear need for close collaboration between computing and clinical experts. We believe that progress will be possible with multidisciplinary collaborative research.

3.
EURASIP J Adv Signal Process ; 2018(1): 33, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29904392

RESUMO

In this paper, we propose a massive MIMO (multiple-input-multiple-output) architecture with distributed steerable phased antenna subarrays for position estimation in the mmWave range. We also propose localization algorithms and a multistage/multiresolution search strategy that resolve the problem of high side lobes, which is inherent in spatially coherent localization. The proposed system is intended for use in line-of-sight indoor environments. Time synchronization between the transmitter and the receiving system is not required, and the algorithms can also be applied to a multiuser scenario. The simulation results for the line-of-sight-only and specular multipath scenarios show that the localization error is only a small fraction of the carrier wavelength and that it can be achieved under reasonable system parameters including signal-to-noise ratios, antenna number/placement, and subarray apertures. The proposed concept has the potential of significantly improving the capacity and spectral/energy efficiency of future mmWave massive MIMO systems.

4.
PLoS One ; 12(9): e0185417, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28953927

RESUMO

In this paper, we propose an application of non-parametric Bayesian (NPB) models for classification of fetal heart rate (FHR) recordings. More specifically, we propose models that are used to differentiate between FHR recordings that are from fetuses with or without adverse outcomes. In our work, we rely on models based on hierarchical Dirichlet processes (HDP) and the Chinese restaurant process with finite capacity (CRFC). Two mixture models were inferred from real recordings, one that represents healthy and another, non-healthy fetuses. The models were then used to classify new recordings and provide the probability of the fetus being healthy. First, we compared the classification performance of the HDP models with that of support vector machines on real data and concluded that the HDP models achieved better performance. Then we demonstrated the use of mixture models based on CRFC for dynamic classification of the performance of (FHR) recordings in a real-time setting.


Assuntos
Frequência Cardíaca Fetal , Teorema de Bayes , Humanos , Modelos Biológicos
5.
IEEE Trans Biomed Eng ; 61(11): 2796-805, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24951678

RESUMO

This paper presents novel methods for classification of fetal heart rate (FHR) signals into categories that are meaningful for clinical implementation. They are based on generative models (GMs) and Bayesian theory. Instead of using scalar features that summarize information obtained from long-duration data, the models allow for explicit use of feature sequences derived from local patterns of FHR evolution. We compare our methods with a deterministic expert system for classification and with a support vector machine approach that relies on system-identification and heart rate variability features. We tested the classifiers on 83 retrospectively collected FHR records, with the gold-standard true diagnosis defined using umbilical cord pH values. We found that our methods consistently performed as well as or better than these, suggesting that the use of GMs and the Bayesian paradigm can bring significant improvement to automatic FHR classification approaches.


Assuntos
Monitorização Fetal/métodos , Frequência Cardíaca Fetal/fisiologia , Processamento de Sinais Assistido por Computador , Teorema de Bayes , Feminino , Humanos , Recém-Nascido , Modelos Estatísticos , Gravidez
6.
Conf Proc IEEE Eng Med Biol Soc ; 2012: 6204-7, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-23367346

RESUMO

We present preliminary results on the use of Bayesian-network (BN) structure learning algorithms for deciphering dependencies from amongst different fetal heart rate (FHR) features collected from a real database. We used a greedy search-and-score procedure known as the K2 algorithm for the estimation of the BN structure. The database consists of a collection of discrete-valued features quantifying presence of morphological changes as prescribed by expert guidelines (updated by the National Institute of Child Health and Human Development (NICHD)) and implemented as rule-based programs. We compare the results of structure learning to the expert-guided structure and use decision functions for classification using posterior probabilities. It was found that the BN estimated from structure learning algorithms had comparable classification performance, but fewer edges, leading to more efficient characterization of conditional probability tables (CPD's). Moreover, structure learning algorithms offer a method of learning novel correlations between FHR features that may be exploited for automatic categorization.


Assuntos
Teorema de Bayes , Frequência Cardíaca Fetal , Aprendizagem , Algoritmos , Feminino , Humanos , Gravidez
7.
Methods Mol Biol ; 711: 421-34, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21279615

RESUMO

Over the past decade, the advances in human brain magnetic resonance imaging (MRI) have significantly improved our ability to gain insightful information about the structure and function of the brain. One of the MRI imaging modalities that still awaits more comprehensive data mining is magnetic resonance spectroscopy (MRS). MRS provides information on the functional status of the brain tissue and can detect metabolic abnormalities that precede structural changes. The chemical specificity of proton MRS ((1)H-MRS) allows detection of several biomarkers that are specific for neurons (N-acetyl aspartate, NAA) and astrocytes (myoinositol (mI) and choline (Cho)), the two most abundant cell types present in the brain tissue. However, apart from a dozen metabolites, current methodologies utilized for MRS analysis do not allow further biomarker discoveries. Herein, we introduce a bioinformatics approach to MRS data processing and discuss possible discoveries that such approach may provide. Specifically, we describe the methodology for neural stem/progenitor cell (NPC) detection in vitro and in vivo, utilizing metabolomic profiling and singular value decomposition analyses.


Assuntos
Imagem por Ressonância Magnética/métodos , Células-Tronco Neurais/citologia , Biologia de Sistemas/métodos , Algoritmos , Animais , Células Cultivadas , Humanos , Espectroscopia de Ressonância Magnética , Metabolômica , Camundongos , Células-Tronco Neurais/metabolismo
8.
BMC Genomics ; 9: 359, 2008 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-18667080

RESUMO

BACKGROUND: Human interfollicular epidermis is sustained by the proliferation of stem cells and their progeny, transient amplifying cells. Molecular characterization of these two cell populations is essential for better understanding of self renewal, differentiation and mechanisms of skin pathogenesis. The purpose of this study was to obtain gene expression profiles of alpha 6+/MHCI+, transient amplifying cells and alpha 6+/MHCI-, putative stem cells, and to compare them with existing data bases of gene expression profiles of hair follicle stem cells. The expression of Major Histocompatibility Complex (MHC) class I, previously shown to be absent in stem cells in several tissues, and alpha 6 integrin were used to isolate MHCI positive basal cells, and MHCI low/negative basal cells. RESULTS: Transcriptional profiles of the two cell populations were determined and comparisons made with published data for hair follicle stem cell gene expression profiles. We demonstrate that presumptive interfollicular stem cells, alpha 6+/MHCI- cells, are enriched in messenger RNAs encoding surface receptors, cell adhesion molecules, extracellular matrix proteins, transcripts encoding members of IFN-alpha family proteins and components of IFN signaling, but contain lower levels of transcripts encoding proteins which take part in energy metabolism, cell cycle, ribosome biosynthesis, splicing, protein translation, degradation, DNA replication, repair, and chromosome remodeling. Furthermore, our data indicate that the cell signaling pathways Notch1 and NF-kappaB are downregulated/inhibited in MHC negative basal cells. CONCLUSION: This study demonstrates that alpha 6+/MHCI- cells have additional characteristics attributed to stem cells. Moreover, the transcription profile of alpha 6+/MHCI- cells shows similarities to transcription profiles of mouse hair follicle bulge cells known to be enriched for stem cells. Collectively, our data suggests that alpha 6+/MHCI- cells may be enriched for stem cells. This study is the first comprehensive gene expression profile of putative human epithelial stem cells and their progeny that were isolated directly from neonatal foreskin tissue. Our study is important for understanding self renewal and differentiation of epidermal stem cells, and for elucidating signaling pathways involved in those processes. The generated data base may serve those working with other human epithelial tissue progenitors.


Assuntos
Perfilação da Expressão Gênica , Folículo Piloso/metabolismo , Queratinócitos/metabolismo , Células-Tronco/metabolismo , Animais , Proliferação de Células , Células Cultivadas , Bases de Dados de Ácidos Nucleicos , Citometria de Fluxo , Expressão Gênica , Genes MHC Classe I , Folículo Piloso/citologia , Humanos , Recém-Nascido , Integrina alfa6/genética , Queratinócitos/citologia , Antígeno Ki-67/genética , Camundongos , NF-kappa B/genética , Análise de Sequência com Séries de Oligonucleotídeos , RNA/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Células-Tronco/citologia , Transcrição Genética
9.
Science ; 321(5889): 640, 2008 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-26380846

RESUMO

We reported on a neural progenitor cell biomarker, a lipid-based metabolite enriched in these cells, which we detected using spectroscopy both in vitro and in vivo, and singular value decomposition­based signal processing. The study provided an outline of our computational methodology. Herein, we report more extensively on the method of spectrum analysis used, demonstrating the specificity of our findings.


Assuntos
Biomarcadores/análise , Encéfalo/citologia , Cognição , Inteligência/genética , Lipídeos/análise , Espectroscopia de Ressonância Magnética/métodos , Mutação , Neurônios/citologia , Esquizofrenia/genética , Células-Tronco/citologia , Animais , Humanos
10.
Science ; 318(5852): 980-5, 2007 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-17991865

RESUMO

The identification of neural stem and progenitor cells (NPCs) by in vivo brain imaging could have important implications for diagnostic, prognostic, and therapeutic purposes. We describe a metabolic biomarker for the detection and quantification of NPCs in the human brain in vivo. We used proton nuclear magnetic resonance spectroscopy to identify and characterize a biomarker in which NPCs are enriched and demonstrated its use as a reference for monitoring neurogenesis. To detect low concentrations of NPCs in vivo, we developed a signal processing method that enabled the use of magnetic resonance spectroscopy for the analysis of the NPC biomarker in both the rodent brain and the hippocampus of live humans. Our findings thus open the possibility of investigating the role of NPCs and neurogenesis in a wide variety of human brain disorders.


Assuntos
Células-Tronco Adultas/citologia , Ácidos Graxos/análise , Hipocampo/citologia , Espectroscopia de Ressonância Magnética/métodos , Neurônios/citologia , Células-Tronco/citologia , Adolescente , Adulto , Células-Tronco Adultas/química , Algoritmos , Animais , Biomarcadores/análise , Biomarcadores/química , Encéfalo/citologia , Encéfalo/embriologia , Química Encefálica , Diferenciação Celular , Criança , Células-Tronco Embrionárias/química , Células-Tronco Embrionárias/citologia , Ácidos Graxos/química , Feminino , Hipocampo/química , Humanos , Masculino , Camundongos , Neurônios/química , Prótons , Ratos , Processamento de Sinais Assistido por Computador , Células-Tronco/química
11.
J Chem Phys ; 122(10): 104101, 2005 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-15836303

RESUMO

We present a general method for the computation of molecular population distributions in a system of first-order chemical reactions. The method is based on the observation that the molecules in first-order reactions do not interact with each other. Therefore, the population distributions are a convolution of densities for one molecule. With this method one can study reactions involving any number of molecules. Such analysis is demonstrated on several examples, including an enzyme catalyst reaction and a first-order reaction chain.

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