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1.
Top Curr Chem (Cham) ; 381(1): 6, 2022 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-36574160

RESUMO

Graphene (G) has been a game-changer for conductive optical devices and has shown promising aspects for its implementation in the power industry due to its diverse structures. Graphene has played an essential role as electrodes, hole transport layers (HTLs), electron transport layers (ETLs), and a chemical modulator for perovskite layers in perovskite solar cells (PSCs) over the past decade. Nitrogen-doped graphene (N-DG) derivatives are frequently evaluated among the existing derivatives of graphene because of their versatility of design, easy synthesis process, and high throughput. This review presents a state-of-the-art overview of N-DG preparation methods, including wet chemical process, bombardment, and high thermal treatment methods. Furthermore, it focuses on different structures of N-DG derivatives and their various applications in PSC applications. Finally, the challenges and opportunities for N-DG derivatives for the continuous performance improvement of PSCs have been highlighted.


Assuntos
Grafite , Compostos de Cálcio , Condutividade Elétrica , Nitrogênio
2.
Spectrochim Acta A Mol Biomol Spectrosc ; 191: 478-490, 2018 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-29091907

RESUMO

Base catalysed ring opening ring closure (RORC) reaction of 6-methylchromone-3­carbonitrile (1) with 1,3-cyclohexanedione afforded 8-methyl-1,2-dihydro-4H-chromeno[2,3-b]quinoline-4,6(3H)-dione (MDCQD). Theoretical calculations by Density Functional Theory (DFT) at the B3LYP/6-311G (d,p) level of theory was utilized to illustrate the equilibrium geometries of MDCQD. Also, the nonlinear optical properties, simple harmonic vibrational frequencies, thermo-chemical parameters and Mullikan atomic charges were calculated. In addition, the electronic absorption spectra in polar and non polar solvents were discussed on the basis of TD-DFT calculations. A nanofiber-like structure with high aggregation was resolved by using scanning electron microscopy images and its particle sizes were measured by particle size analyzer. The spectroscopic characteristics of the prepared thin film of MDCQD were studied in a wide spectral range of 200-2500nm. The analysis of the absorption edges affords two direct optical band gaps with energies of 1.00 and 2.76eV. A characteristic emission peak of photoluminescence spectrum in the visible region was detected and has a red-shift as a result of solvent polarity. The MDCQD film based heterojunction showed rectification behavior and diode-like characteristics. The photovoltaic characteristics under illumination of 100mW/cm2 were studied. The open-circuit voltage and short-circuit current were found to be 0.22V and 4.25×10-7A/cm2, respectively. Moreover, the prepared heterojunction showed remarkable phototransient characteristics which afford the probability for the operation as a photodiode.

3.
Spectrochim Acta A Mol Biomol Spectrosc ; 152: 218-25, 2016 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-26218916

RESUMO

In this work, a new synthesized mononuclear mixed ligand nickel(II) complex was characterized by various techniques. Crystalline characteristics of [Ni(Phth)(Me4en)(H2O)2]·4H2O were studied by using transmission electron microscope(TEM). Well crystalline structure corresponds to the hexagonal crystal system and identified by selected area electron diffraction (SAED) were achieved. Coordination of the nickel(II) ion with the functional groups of the ligands was established from the IR spectrum. Molar conductance of the current complex in DMF (10(-3)mol/L) indicated a non-electrolytic nature of the complex. Electronic spectra showed a strong band in the region 661-684nm; MeCN (661nm), CHCl3 (663nm), MeOH (667nm), Me2CO (675nm), DMSO (682nm) and DMF (684nm) which can be assigned to (3)A2g(F)→(3)T1g(F) transition of an octahedral structure around nickel(II). Multiple peaks were easily resolved from the spectral dependence of the absorption coefficient (α) measurements and the analysis near the fundamental absorption edge showed two direct allowed transition with energy gaps of 1.18 and 2.53eV. Dark current-voltage and capacitance-voltage characteristics of [Ni(Phth)(Me4en)(H2O)2]·4H2O/n-Si heterojunctions were studied to extract the main important parameters of the heterojunction device. The electrical characteristics of the heterojunction device under illumination hold the suitability of the device for optoelectronic applications.

4.
Drug Res (Stuttg) ; 65(7): 373-9, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25116255

RESUMO

This article describes the synthesis of novel 5-(morpholinosulfonyl)isatin derivatives having biologically active thiazole moiety were synthesized via 2 synthetic routes. The first route involved interaction of 5-(morpholino-sulfonyl) isatin with aminothiazole derivatives to give the Schiff's base derivatives (2, 3). The second route involved preparation of thiosemicarbazones (4-7) by treatment of 5-(morpholino- sulfonyl) isatin with thiosemicarbazides followed by cycloalkylation of the products with halogenated compounds to give the thiazole derivatives (8-19). Most of the synthesized compounds were screened against Gram (+), Gram (-) bacterial and fungi. The best gram positive activity was displayed by compounds 1, 13, 14, 15, 16 and 18 and the best gram negative bacteria was showed by compounds 1, 12, 13, 15, and 19, whereas compounds 1, 12, 13, 15, and 19 exhibited the best antifungal activity.


Assuntos
Antibacterianos/síntese química , Antibacterianos/farmacologia , Antifúngicos/síntese química , Antifúngicos/farmacologia , Isatina/análogos & derivados , Isatina/síntese química , Tiazóis/síntese química , Isatina/farmacologia , Testes de Sensibilidade Microbiana , Relação Estrutura-Atividade , Tiazóis/farmacologia
5.
Spectrochim Acta A Mol Biomol Spectrosc ; 130: 494-501, 2014 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-24813278

RESUMO

A new binuclear mixed ligand complex, [Cu2(Phth)(Me4en)2(H2O)2(NO3)2]·H2O (where, Phth=phthalate, and (Me4en)=N,N,N',N'tetramethylethylenediamine) was synthesized and characterized using analytical, spectral, magnetic, molar conductance, thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements. The XRD data of Cu(II)-complex was analyzed on the basis of Williamson-Hall (W-H) and compared with TEM results. The results indicate that the complex is well crystalline and correspond to hexagonal crystal structure. Analysis of the absorption coefficient near the absorption edge reveals that the optical band gaps are indirect allowed transition with values of 1.17 and 1.78 eV. The d-d absorption bands of the complex (dissolved in various solvents) exhibit a color changes (solvatochromic). Specific and non-specific interactions of solvent molecules with the complex were investigated using Multiple Linear Regression Analysis (MLRA). Transient photocurrent characteristics of Cu(II)-complex/n-Si heterojunctions indicate that photocurrent under illumination increase with increasing of light intensity and explained by continuous distribution of traps. Structural parameters of the free ligands and their Cu(II)-complex were calculated on the basis of semi-empirical PM3 level and compared with the experimental data. The present copper (II) complex was screened for its antimicrobial activity against some Gram-positive and Gram-negative bacteria and fungus strain.


Assuntos
Cobre/química , Etilenodiaminas/química , Espectrofotometria Infravermelho , Anti-Infecciosos/química , Cristalização , Condutividade Elétrica , Temperatura Alta , Ligantes , Modelos Lineares , Testes de Sensibilidade Microbiana , Microscopia Eletrônica de Transmissão , Óptica e Fotônica , Fotoquímica , Solventes/química , Termogravimetria , Difração de Raios X
6.
Spectrochim Acta A Mol Biomol Spectrosc ; 122: 512-20, 2014 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-24334014

RESUMO

In this work, a new solvatochromic mononuclear mixed ligand complex with the formula, Cu(DMCHD)(Me5dien)NO3 (where, DMCHD=5,5-Dimethyl cyclohexanate 1,3-dione and (Me5dien)=N,N,N',N'N″-pentamethyldiethylenetriamine was synthesized and characterized by analytical, spectral, magnetic, molar conductance, thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements. The formation constant-value for copper (II)-DMCHD was found to be much lower than the expected for similar ß-diketones, revealing monobasic unidentate nature of this ligand. The d-d absorption bands of the prepared complex exhibit a color changes in various solvent (solvatochromic). Specific and non-specific interactions of solvent molecules with the complex were investigated using Multi Parametric Linear Regression Analysis (MLRA). Structural parameters of the free ligands and their Cu (II) - complex were calculated on the basis of semi-empirical PM3 level and compared with the experimental data. The crystallite size and morphology of Cu(DMCHD)(Me5dien)NO3 were examined using XRD analysis and TEM, revealing that the complex is well crystalline and correspond to the monoclinic crystal structure. The lattice strain and mean crystallite size were estimated by Williamson-Hall (W-H) plot using X-ray diffraction data. The main important absorption parameters such as extinction molar coefficient, oscillator strength and electric dipole strength of the principal optical transitions in the UV-Vis region were calculated. The analysis of absorption coefficient near the fundamental absorption edge reveals that the optical band gaps are direct allowed transitions with values of 2.78 eV and 3.59 eV. The present copper (II) complex was screened for its antimicrobial activity against Staphylococcus Aureus and Bacillus Subtilis as Gram-positive bacteria, Escherichia Coli and Salmonella Typhimurium as Gram-negative bacteria and Candida Albicans as fungus strain.


Assuntos
Anti-Infecciosos/química , Complexos de Coordenação/química , Cobre/química , Cicloexanos/química , Poliaminas/química , Anti-Infecciosos/farmacologia , Bactérias/efeitos dos fármacos , Infecções Bacterianas/tratamento farmacológico , Candida albicans/efeitos dos fármacos , Candidíase/tratamento farmacológico , Complexos de Coordenação/farmacologia , Cobre/farmacologia , Cicloexanos/farmacologia , Humanos , Ligantes , Testes de Sensibilidade Microbiana , Modelos Moleculares , Poliaminas/farmacologia , Difração de Raios X
7.
Artigo em Inglês | MEDLINE | ID: mdl-23557769

RESUMO

Zinc(II)-8-hydroxy-5-nitrosoquinolate, [Zn(II)-(HNOQ)2], was synthesized and assembled as a deposited thin film of nano-metal complex by a rapid, direct, simple and efficient procedure based on layer-by-layer chemical deposition technique. Stoichiometric identification and structural characterization of [Zn(II)-(HNOQ)2] were confirmed by electron impact mass spectrometry (EI-MS) and Fourier Transform infrared spectroscopy (FT-IR). Surface morphology was studied by using a scanning electron microscope imaging (SEM) and the particle size was found to be in the range of 23-49 nm. Thermal stability of [Zn(II)-(HNOQ)2] was studied and the thermal parameters were evaluated using thermal gravimetric analysis (TGA). The current density-voltage measurements showed that the current flow is dominated by a space charge limited and influenced by traps under high bias. The optical properties of [Zn(II)-(HNOQ)2] thin films were found to exhibit two direct allowed transitions at 2.4 and 1.0 eV, respectively.


Assuntos
Complexos de Coordenação/química , Nanoestruturas/química , Compostos Nitrosos/química , Ácido Quinolínico/química , Zinco/química , Nanoestruturas/ultraestrutura , Espectrometria de Massas por Ionização por Electrospray , Espectroscopia de Infravermelho com Transformada de Fourier , Termogravimetria
8.
Artigo em Inglês | MEDLINE | ID: mdl-23220530

RESUMO

Nano Al(III)-8-hydroxy-5-nitrosoquinolate [Al(III)-(HNOQ)(3)] thin films were synthesized by the rapid, direct, simple and efficient successive ion layer adsorption and reaction (SILAR) technique. Thin film formation optimized factors were evaluated. Stoichiometry and structure were confirmed by elemental analysis and FT-IR. The particle size (27-71 nm) was determined using scanning electron microscope (SEM). Thermal stability and thermal parameters were determined by thermal gravimetric analysis (TGA). Optical properties were investigated using spectrophotometric measurements of transmittance and reflectance at normal incidence. Refractive index, n, and absorption index, k, were determined. Spectral behavior of the absorption coefficient in the intrinsic absorption region revealed a direct allowed transition with 2.45 eV band gap. The current-voltage (I-V) characteristics of [Al(III)-(HNOQ)(3)]/p-Si heterojunction was measured at room temperature. The forward and reverse I-V characteristics were analyzed. The calculated zero-bias barrier height (Φ(b)) and ideality factor (n) showed strong bias dependence. Energy distribution of interface states (N(ss)) was obtained.


Assuntos
Alumínio/química , Complexos de Coordenação/química , Nanoestruturas/química , Compostos Nitrosos/química , Ácido Quinolínico/química , Adsorção , Complexos de Coordenação/síntese química , Íons/síntese química , Íons/química , Nanoestruturas/ultraestrutura , Nanotecnologia , Compostos Nitrosos/síntese química , Ácido Quinolínico/síntese química , Refratometria , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Termogravimetria
9.
Artigo em Inglês | MEDLINE | ID: mdl-22465777

RESUMO

A method is described for thin film assembly of nano-sized Zn(II)-8-hydroxy-5,7-dinitroquinolate complex, Zn[((NO(2))(2)-8HQ)(2)] by using successive ion layer adsorption and reaction (SILAR) technique. Highly homogeneous assembled nano-sized metal complex thin films with particle size distribution in the range 27-47nm was identified by using scanning electron microscopy (SEM). Zn[((NO(2))(2)-8HQ)(2)] and [(NO(2))(2)-8HQ] ligand were studied by thermal gravimetric analysis (TGA). Graphical representation of temperature dependence of the dark electrical conductivity produced two distinct linear parts for two activation energies at 0.377eV and 1.11eV. The analysis of the spectral behavior of the absorption coefficient in the intrinsic absorption region reveals a direct allowed transition with a fundamental band gap of 2.74eV. The dark current density-voltage (J-V) characteristics showed the rectification effect due to the formation of junction barrier of Zn[((NO(2))(2)-8HQ)(2)] complex film/n-Si interface. The photocurrent in the reverse direction is strongly increased by photo-illumination and the photovoltaic characteristics were also determined and evaluated.


Assuntos
Nanoestruturas/química , Compostos Organometálicos/química , Adsorção , Condutividade Elétrica , Nanoestruturas/ultraestrutura , Tamanho da Partícula , Espectrofotometria , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Termogravimetria
10.
Artigo em Inglês | MEDLINE | ID: mdl-21855401

RESUMO

Spectral-optical-electrical-thermal properties of deposited thin films of nano-sized calcium(II)-8-hydroxy-5,7-dinitroquinolate complex, Ca[((NO(2))(2)-8HQ)(2)], were explored, studied and evaluated in this work. Thin films of Ca[((NO(2))(2)-8HQ)(2)] were assembled by using a direct, simple and efficient layer-by-layer (LBL) chemical deposition technique. The optical properties of thin films were investigated by using spectrophotometric measurements of transmittance and reflectance at normal incidence in the wavelength range 200-2500 nm. The refractive index, n, and the absorption index, k, of Ca[((NO(2))(2)-8HQ)(2)] films were determined from the measured transmittance and reflectance. The real and imaginary dielectric constants were also determined. The analysis of the spectral behavior of the absorption coefficient in the intrinsic absorption region reveals a direct allowed transition with band gaps of 1.1 eV and 2.4 eV for the optical and transport energy gaps, respectively. The current-voltage characteristics of Ca[((NO(2))(2)-8HQ)(2)] showed a trap-charge limited conduction in determining the current at the intermediate and high bias regimes. Graphical representation of the current-voltage characteristics yields three distinct linear parts indicating the existence of three conduction mechanisms. Structural characterization and identification were confirmed by using Fourier transform infrared spectroscopy (FT-IR). Scanning electron microscopy (SEM) was also used to image the surface morphology of the deposited nano-sized metal complex and such study revealed a high homogeneity in surface spherical particle distribution with average particles size in the range 20-40 nm. Thermal gravimetric analysis (TGA) was also studied for [(NO(2))(2)-8HQ] and Ca[((NO(2))(2)-8HQ)(2)] to evaluate and confirm the thermal stability characteristics incorporated into the synthesized nano-sized Ca[((NO(2))(2)-8HQ)(2)] complex.


Assuntos
Cálcio/química , Nanotecnologia/métodos , Quinolinas/química , Cristalização , Eletrônica , Temperatura Alta , Ligantes , Microscopia Eletrônica de Varredura/métodos , Modelos Químicos , Modelos Estatísticos , Nanoestruturas/química , Óptica e Fotônica/métodos , Oscilometria , Refratometria , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Termogravimetria/métodos
11.
Environ Toxicol Pharmacol ; 30(2): 110-5, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21787639

RESUMO

Fakous Province in the Sharkia Governorate constitutes one of the largest agricultural areas in Egypt. The majority of people in this province rely on subsistence agriculture. In the cotton cultivation season the continuous application of pesticides is commonly used to increase agricultural productivity, using different types of spraying equipment. In this study a cohort of 210 intensive agricultural pesticide applicators and farm workers from Sawada and Akyad Elkepplia villages in Fakous Province were assessed according to the type of spraying equipment they used. Conventional motor (300l/feddan or 0.42ha) and knapsack motor sprayer (20l/feddan) were commonly used by farmers. Contamination on applicators was detected on head, body (thorax/abdomen) and legs at different percentages according to the spraying tools. The recorded results revealed that contamination with pesticides due to knapsack motor sprayers 0.76% on head, 4.8% on body and 5.8% on legs; however, conventional motor sprayers induce contamination of 3.6% on head, 23.7% on body and 29.1% on legs. Several criteria for estimating pesticide contamination by previous delivery systems were used. The most important reference biomarker was serum acetyl cholinesterase (AchE) depression. Sprayers showed changes in serum glucose levels as well as reduced erythrocytic glutathione levels (GSH). However, an increase in both total serum protein and albumin was recorded also, alongside elevation in lipid peroxidation biomarker malondialdehyde (MDA). Changes in serum biochemistry regarding enzymes reflecting cytotoxicity were also recorded, such as inhibition of alanine aminotransferase (ALT) and glutathione-S-transferase (GST). An increase in aspartate aminotransferase (AST) and glutathione reductase (GR) was observed particularly in conventional motor sprayers. Changes in enzymes activities found in this study are linked to the adverse health effects related to chronic pesticide toxicity that may lead to pathophysiological diseases, cancer or neurodegenerative disorders, which warrants further investigation.

12.
Artigo em Inglês | MEDLINE | ID: mdl-17482509

RESUMO

Thin films of 4-tricyanovinyl-N,N-diethylaniline (TCVA) were prepared for the first time using thermal evaporation technique. The molecular structure and electronic transitions of TCVA films were investigated by Fourier-transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectra. The observed vibrational wavenumbers in FTIR spectra were analysed and assigned to different normal modes of the molecule. UV-vis electronic absorption spectral measurements of TCVA films were analysed to obtain the electronic transitions and optical band gap (E(g)). Other important optical parameters such as molar extinction coefficient (epsilon(molar)), the oscillator strength (f), and the electric dipole strength (q(2)) were also reported.


Assuntos
Compostos de Anilina/química , Nitrilas/química , Óptica e Fotônica , Arsênio/química , Varredura Diferencial de Calorimetria , Elétrons , Espectroscopia de Infravermelho com Transformada de Fourier
13.
Arch Pharm (Weinheim) ; 340(11): 591-8, 2007 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17924363

RESUMO

New heterocyclic compounds containing pyrazol-5-one coupled with benzimidazole, benzothiazole, benzoxazole, quinoline, naphthyridin, and pyrazole were synthesized. Comparative investigations to synthesize these interesting classes of heterocyclic compounds through conventional heating or under microwave-irradiation conditions were presented. Synthesized compounds 1a, 2a, 4k, 3a, c, 5a, b, 6b, 7a, b, d, 8a, and 9a were evaluated for their antitumor activity. Some of these compounds exhibited promising antitumor activity.


Assuntos
Antineoplásicos , Micro-Ondas , Pirazóis , Animais , Antineoplásicos/síntese química , Antineoplásicos/química , Antineoplásicos/farmacologia , Antineoplásicos/uso terapêutico , Carcinoma de Ehrlich/tratamento farmacológico , Carcinoma de Ehrlich/patologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Desenho de Fármacos , Ensaios de Seleção de Medicamentos Antitumorais , Feminino , Camundongos , Pirazóis/síntese química , Pirazóis/química , Pirazóis/farmacocinética , Pirazóis/uso terapêutico , Solventes , Fatores de Tempo
14.
IEEE Trans Pattern Anal Mach Intell ; 29(9): 1563-74, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17627044

RESUMO

A wide range of computer vision applications require an accurate solution of a particular Hamilton- Jacobi (HJ) equation, known as the Eikonal equation. In this paper, we propose an improved version of the fast marching method (FMM) that is highly accurate for both 2D and 3D Cartesian domains. The new method is called multi-stencils fast marching (MSFM), which computes the solution at each grid point by solving the Eikonal equation along several stencils and then picks the solution that satisfies the upwind condition. The stencils are centered at each grid point and cover its entire nearest neighbors. In 2D space, 2 stencils cover the 8-neighbors of the point, while in 3D space, 6 stencils cover its 26-neighbors. For those stencils that are not aligned with the natural coordinate system, the Eikonal equation is derived using directional derivatives and then solved using higher order finite difference schemes. The accuracy of the proposed method over the state-of-the-art FMM-based techniques has been demonstrated through comprehensive numerical experiments.


Assuntos
Algoritmos , Inteligência Artificial , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Armazenamento e Recuperação da Informação/métodos , Reconhecimento Automatizado de Padrão/métodos , Análise Numérica Assistida por Computador , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
15.
Spectrochim Acta A Mol Biomol Spectrosc ; 65(3-4): 667-72, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16527532

RESUMO

The optical absorption studies of sodium copper chlorophyllin thin films (SCC), prepared by spray pyrolysis, in the UV-vis-NIR region was reported for the first time. Several new discrete transitions are observed in the UV-vis region of the spectra in addition to a strong continuum component in the IR region. The spectra of the infrared absorption allow characterization of vibration modes for the powder and thin films of SCC. The absorption spectrum recorded in the UV-vis region showed different absorption bands, namely the Soret (B) in the region 340-450 nm and Q-band in the region 600-700 nm and other band labeled N in the 240-320 region. Some important spectral parameters namely optical absorption coefficient (alpha), molar extinction coefficient (epsilon(molar)), oscillator strength (f), electric dipole strength (q(2)) and absorption half bandwidth (Deltalambda) of the principle optical transitions were evaluated. The analysis of the absorption coefficient in the absorption region revealed direct transitions and the energy gap was estimated as 1.63 eV. Discussion of the obtained results and their comparison with the previous published data are also given.


Assuntos
Clorofilídeos/química , Absorção , Cobre/química , Estrutura Molecular , Óptica e Fotônica , Sódio/química , Espectrofotometria Infravermelho , Espectrofotometria Ultravioleta , Vibração
16.
Med Image Anal ; 10(1): 2-18, 2006 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-15893953

RESUMO

In this paper, we present an automatic statistical approach for extracting 3D blood vessels from time-of-flight (TOF) magnetic resonance angiography (MRA) data. The voxels of the dataset are classified as either blood vessels or background noise. The observed volume data is modeled by two stochastic processes. The low level process characterizes the intensity distribution of the data, while the high level process characterizes their statistical dependence among neighboring voxels. The low level process of the background signal is modeled by a finite mixture of one Rayleigh and two normal distributions, while the blood vessels are modeled by one normal distribution. The parameters of the low level process are estimated using the expectation maximization (EM) algorithm. Since the convergence of the EM is sensitive to the initial estimate of the model parameters, an automatic method for parameter initialization, based on histogram analysis, is provided. To improve the quality of segmentation achieved by the proposed low level model especially in the regions of significantly vascular signal loss, the high level process is modeled as a Markov random field (MRF). Since MRF is sensitive to edges and the intracranial vessels represent roughly 5% of the intracranial volume, 2D MRF will destroy most of the small and medium sized vessels. Therefore, to reduce this limitation, we employed 3D MRF, whose parameters are estimated using the maximum pseudo likelihood estimator (MPLE), which converges to the true likelihood under large lattice. Our proposed model exhibits a good fit to the clinical data and is extensively tested on different synthetic vessel phantoms and several 2D/3D TOF datasets acquired from two different MRI scanners. Experimental results showed that the proposed model provides good quality of segmentation and is capable of delineating vessels down to 3 voxel diameters.


Assuntos
Encéfalo/irrigação sanguínea , Processamento de Imagem Assistida por Computador , Imageamento Tridimensional , Angiografia por Ressonância Magnética , Modelos Estatísticos , Algoritmos , Angiografia Cerebral , Humanos , Imagens de Fantasmas , Processamento de Sinais Assistido por Computador , Processos Estocásticos
17.
Artigo em Inglês | MEDLINE | ID: mdl-17354913

RESUMO

In this paper, we propose a new visualization technique for virtual colonoscopy (VC). The proposed method is called Virtual Fly-Over, which splits the entire colon anatomy into exactly two halves. Then, it assigns a virtual camera to each half to perform fly-over navigation, which has several advantages over both traditional fly-through and related methods. First, by controlling the elevation of the camera, there is no restriction on its field of view (FOV) angle (e.g., >90 degrees) to maximize visualized surface areas, and hence no perspective distortion. Second, the camera viewing volume is perpendicular to each colon half, so potential polyps that are hidden behind haustral folds are easily found. Finally, because the orientation of the splitting surface is controllable, the navigation can be repeated at a different split orientation to overcome the problem of having a polyp that is divided between the two halves of the colon. Quantitative experimental results on 15 clinical datasets have shown that the average surface visibility coverage is 99.59 +/- 0.2%.


Assuntos
Algoritmos , Colonografia Tomográfica Computadorizada/métodos , Gráficos por Computador , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Interface Usuário-Computador , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
18.
Inf Process Med Imaging ; 19: 529-40, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-17354723

RESUMO

Three dimensional medial paths or curve skeletons (CS) are an essential component of any virtual endoscopy (VE) system, because they serve as flight paths for a virtual camera to navigate the human organ and to examine its internal structures. In this paper, we propose a novel framework for computing flight paths of tubular structures for VE using partial differential equation (PDE). The method works in two passes. In the first pass, the overall topology of the organ is analyzed and its important topological nodes are identified, while in the second pass, the actual flight paths are computed by tracking them starting from each identified node. The proposed framework is robust, fully automatic, computationally efficient, and computes CS that are centered, connected, thin, and less sensitive to boundary noise. We have extensively validated the robustness of the proposed method both quantitatively and qualitatively against several synthetic phantoms and clinical datasets.


Assuntos
Endoscopia/métodos , Imageamento Tridimensional/métodos , Modelos Biológicos , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Interface Usuário-Computador , Algoritmos , Inteligência Artificial , Simulação por Computador , Humanos , Aumento da Imagem/métodos , Imagens de Fantasmas , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Tomografia Computadorizada por Raios X/instrumentação
19.
Orthod Craniofac Res ; 6 Suppl 1: 108-16; discussion 179-82, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-14606543

RESUMO

OBJECTIVES: To present two practical techniques for three-dimensional (3D) modeling of the human jaw from a sequence of intra-oral images. DESIGN: A data acquisition system consists of: 3D digitizing arm, CCD camera and a laser projector in addition to a software module of two 3D modeling techniques; shape from shading (SFS) and space carving (SC). SETTING AND SAMPLE POPULATION: Several experiments have been conducted on a sample of students at the Computer Vision and Image Processing (CVIP) Laboratory at the University of Louisville, Louisville, KY. Other experiments were performed on solid models of human jaw. EXPERIMENTAL VARIABLE: The SFS technique, using perspective projection and camera calibration, extracts the 3D information from a sequence of two-dimensional images of the jaw. Data fusion of range data and 3D registration techniques develop the complete jaw model. The SC approach is implemented on a sequence of calibrated images. On the two reconstructions, we fit a mesh model to the data, in order to create a solid 3D model. OUTCOME MEASURE: The accuracy of the reconstructed 3D model of human jaw is calculated based on the measurements on real jaws. RESULTS: The SFS-based technique seems to provide more faithful information about the shape of the tooth tops. However, the SC algorithm successfully reconstructed 3D models of the human jaw with sub-millimeter accuracy, which is as accurate as (or even better than) the first technique without using any range measurements or laser projectors. The average error in distance calculation was found to be 0.74 mm, which is an acceptable resolution for many orthodontics and maxillofacial applications. CONCLUSION: Accurate 3D reconstruction of the human jaw enables many orthodontics and dental imaging research findings to be applied directly to a digital jaw model--not to a cast--using computer vision and medical imaging tools.


Assuntos
Processamento de Imagem Assistida por Computador , Mandíbula/anatomia & histologia , Gravação em Vídeo , Algoritmos , Cefalometria , Simulação por Computador , Humanos , Imageamento Tridimensional , Lasers , Modelos Anatômicos , Modelos Biológicos , Fotografia Dentária
20.
IEEE Trans Med Imaging ; 19(5): 538-47, 2000 May.
Artigo em Inglês | MEDLINE | ID: mdl-11021697

RESUMO

This paper presents a model-based vision system for dentistry that will assist in diagnosis, treatment planning, and surgical simulation. Dentistry requires an accurate three-dimensional (3-D) representation of the teeth and jaws for diagnostic and treatment purposes. The proposed integrated computer vision system constructs a 3-D model of the patient's dental occlusion using an intraoral video camera. A modified shape from shading (SFS) technique, using perspective projection and camera calibration, extracts the 3-D information from a sequence of two-dimensional (2-D) images of the jaw. Data fusion of range data and 3-D registration techniques develop the complete jaw model. Triangulation is then performed, and a solid 3-D model is reconstructed. The system performance is investigated using ground truth data, and the results show acceptable reconstruction accuracy.


Assuntos
Algoritmos , Oclusão Dentária , Processamento de Imagem Assistida por Computador , Arcada Osseodentária , Óptica e Fotônica , Fotografia Dentária , Calibragem , Simulação por Computador , Humanos , Modelos Dentários , Fotografia Dentária/instrumentação , Pesquisa , Software , Gravação em Vídeo/instrumentação
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