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1.
Inorg Chem ; 62(41): 16890-16897, 2023 Oct 16.
Artículo en Inglés | MEDLINE | ID: mdl-37787977

RESUMEN

Four new noncentrosymmetric tellurites of quaternary A/M/Te/O (A = Ba, Sr, Ca; M = V, Nb, Ta) system, namely, BaTa4Te3O17 (1), BaNb4Te3O17 (2), SrTa4Te3O17 (3), and CaV2TeO8 (4), were synthesized and characterized by single-crystal X-ray diffraction, thermal analysis, diffuse reflectance spectroscopy, and powder second harmonic generation (SHG) response measurements. The isostructural compounds 1-3 crystallize in the P212121 space group and have a three-dimensional (Ta4Te3O17)2-/(Nb4Te3O17)2- anionic framework, whereas the layered compound 4 crystallizes in the Ccc2 space group and has a [V2TeO8]2- anionic layer. The phase-matching compounds 1, 2, and 3 and the non-phase-matching compound 4 show powder SHG responses equivalent to ∼27, ∼13, ∼24, and ∼68% of that of LiNbO3, respectively.

2.
J Contemp Dent Pract ; 20(9): 1067-1070, 2019 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-31797831

RESUMEN

AIM: To evaluate the effect of instrumentation kinematics on debris extrusion by comparing the amount of apically extruded debris after canal preparation using ProTaper next in continuous rotation as well as forward reciprocating motion and WaveOne gold in reverse reciprocating motion. MATERIALS AND METHODS: We randomly divided ninety buccal roots of maxillary bicuspids with fully formed apices into three groups. After achieving the coronal access, the patency of the root canals was established with a size 10 K file. The canals were then instrumented using ProTaper next in continuous rotation or in a forward reciprocating motion and WaveOne gold in reverse reciprocating motion. Eppendorf tubes were used to collect the debris extruded through the apical foramen. The tubes were placed in a -80° freezer for 8 hours and then in a lyophilizer for 24 hours. The quantity of the apically extruded debris was assessed by subtracting the weights of Eppendorf tubes before and after instrumentation. The analysis was done using a one-way ANOVA test and the Bonferroni test to compare the groups. RESULTS: The mean weight of extruded debris with WaveOne gold in reverse reciprocation was significantly lower than ProTaper next in forward reciprocation and ProTaper next in continuous rotation (p value = <0.001). CONCLUSION: WaveOne gold in reverse reciprocation was associated with a significantly lower amount of apical extrusion of debris than ProTaper next rotary files in forward reciprocation and continuous rotation. CLINICAL SIGNIFICANCE: According to the results of this study, reciprocating instrumentation technique was associated with a less amount of debris extrusion compared to continuous rotation.


Asunto(s)
Cavidad Pulpar , Preparación del Conducto Radicular , Diente Premolar , Fenómenos Biomecánicos , Ápice del Diente
3.
Inorg Chem ; 56(20): 12631-12640, 2017 Oct 16.
Artículo en Inglés | MEDLINE | ID: mdl-28968081

RESUMEN

Five isomorphous AM2V2O11 vanadates of niobium and tantalum, namely, BaNb2V2O11, BaTa2V2O11, SrNb2V2O11, SrTa2V2O11, and PbTa2V2O11, were prepared by solid-state reactions and structurally characterized by single-crystal and powder X-ray diffraction techniques. Barium and strontium compounds, respectively, have centrosymmetric and noncentrosymmetric types of layered structure, wherein [M2V2O11]2- anionic layers are interleaved with A2+ cations. Both types of layered structure are found for lead compound. The strontium and lead compounds are type I phase-matching materials with second-harmonic-generating efficiencies of 33-50% of LiNbO3, and their dielectric properties were evaluated. A three-dimensional structural variant was also identified for strontium compounds, which crystallize in noncentrosymmetric orthorhombic space group C2221.

4.
Clin Exp Dermatol ; 42(8): 881-886, 2017 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-28748571

RESUMEN

Porokeratosis, a disorder of keratinisation, is clinically characterized by the presence of annular plaques with a surrounding keratotic ridge. Clinical variants include linear, disseminated superficial actinic, verrucous/hypertrophic, disseminated eruptive, palmoplantar and porokeratosis of Mibelli (one or two typical plaques with atrophic centre and guttered keratotic rim). All of these subtypes share the histological feature of a cornoid lamella, characterized by a column of 'stacked' parakeratosis with focal absence of the granular layer, and dysmaturation (prematurely keratinised cells in the upper spinous layer). In recent years, a proposed new subtype, follicular porokeratosis (FP_, has been described, in which the cornoid lamella are exclusively located in the follicular ostia. We present four new cases that showed typical histological features of FP.


Asunto(s)
Folículo Piloso/patología , Poroqueratosis/patología , Piel/patología , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Lentigo/complicaciones , Lentigo/patología , Masculino , Persona de Mediana Edad , Poroqueratosis/clasificación , Poroqueratosis/complicaciones
5.
J Conserv Dent ; 26(1): 113-117, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-36908734

RESUMEN

Dental trauma results in various complications and poses an enigma to the practitioner. Calcific metamorphosis is one of the sequelae of trauma. A female patient of 35 years visited the specialty clinic of endodontics for the management of a discolored tooth. Clinically, discolored 21 was observed with no pain on palpation and percussion. The pulp sensibility test revealed a negative response. Radiographic examination revealed pulp canal obliteration with an apical radiolucency of Peri Apical Index (PAI 4). The tooth was diagnosed as necrotic pulp with asymptomatic apical periodontitis. Attempt to negotiate the canal under a Dental Operating Microscope (LABOMED, Los Angeles, CA, USA) and ultrasonics (Satelec, Acteon, France) was futile. Cone-beam computed tomography image revealed a patent canal in the apical third. Using real-time guided endodontics with a dynamic navigation system (Navident, ClaroNav, Toronto, ON, Canada), the protocol of plan, trace, and place was followed, and successful canal negotiation was achieved. After radiographic confirmation, root canal treatment was completed.

6.
J Contemp Dent Pract ; 13(6): 764-8, 2012 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-23404000

RESUMEN

AIM: The aim is to compare and evaluate the airway dimension changes, adenoidal nasopharyngeal ratio (ANR), airway area and airway percentage in patients in pre- and postadenoidectomy with normal individuals. MATERIALS AND METHODS: After obtaining informed consent, a sample of 15 patients (eight males and seven females) of 7 to 12 years were selected for adenoidectomy by an otolaryngologist, lateral cephalograms were taken in natural head position before adenoidectomy and after 1 month postadenoidectomy. Statastical analysis was done to evaluate the results using Statastical Package for Social Sciences. Results showed airway (P1, P2, P3, P4), airway percentage, airway area showed significant increase (p < 0.0001), whereas ANR showed significant reduction after 1 month postadenoidectomy. CONCLUSION: One month postadenoidectomy showed increased airway area, airway percentage and reduced ANR. CLINICAL SIGNIFICANCE: Obstructive mouth breathing due to adenoids in growing children can cause alteration in craniofacial morphology leading to adenoid facies, adenoidectomy procedure helps in alleviating the obstruction and facilitates the normal growth of craniofacial complex.


Asunto(s)
Adenoidectomía/métodos , Cefalometría/métodos , Nasofaringe/patología , Orofaringe/patología , Tonsila Faríngea/patología , Obstrucción de las Vías Aéreas/patología , Niño , Femenino , Estudios de Seguimiento , Humanos , Hipertrofia , Masculino , Respiración por la Boca/patología
7.
J Contemp Dent Pract ; 13(1): 85-97, 2012 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-22430700

RESUMEN

INTRODUCTION: Transversal slicing system (TSS) of Planmeca PM 2002 CC is a tomographic technique which enables us to take cross-sectional views of jaws. Tomographic imaging modalities are commonly applied to acquire cross-sectional images of the jaws for preimplant assessment of bone. Among the available tomographic imaging modalities, panoramic radiography is the most accessible imaging system. MATERIALS AND METHODS: Study was conducted using 25 mandibles, out of these five were used for linear dimensional accuracy measurement and the rest 20 were utilized to study the details within the mandible. Study was aimed to evaluate dimensional stability in the images using different parameters, such as determination of direction of slice, determination of horizontal and vertical magnification, angular distortion, three dimensional distortion and determination of details. RESULTS: For the direction of slice and for determination of horizontal and vertical magnification change in + 5º to - 5º was in acceptable limit. In determination of details, it was found that there was great discrepancy in readings given by nonradiologist which offset the mean value which was attributed to lack of training for interpretation of the observers. CONCLUSION: 99% of the readings were in the clinically acceptable limits. CLINICAL SIGNIFICANCE: The easy availability, use of routine equipment, the low cost, low radiation dose for cross-sectional radiography make the TSS most preferred modality.


Asunto(s)
Procesamiento de Imagen Asistido por Computador/estadística & datos numéricos , Mandíbula/diagnóstico por imagen , Radiografía Panorámica/estadística & datos numéricos , Tomografía por Rayos X/estadística & datos numéricos , Puntos Anatómicos de Referencia/anatomía & histología , Puntos Anatómicos de Referencia/diagnóstico por imagen , Anatomía Transversal , Artefactos , Cefalometría/estadística & datos numéricos , Humanos , Imagenología Tridimensional/estadística & datos numéricos , Mandíbula/anatomía & histología , Variaciones Dependientes del Observador , Curva ROC , Intensificación de Imagen Radiográfica , Magnificación Radiográfica/estadística & datos numéricos , Reproducibilidad de los Resultados
8.
J Conserv Dent ; 25(2): 151-155, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35720820

RESUMEN

Background: Peri-cervical dentin (PCD) and its reinforcement play a crucial role in the fracture resistance of root canal-treated teeth. Aims: The aim of this study was to compare the fracture resistance of dual-cure, nano-hybrid, and short-fiber reinforced composite resins restored PCD with conventional hybrid composite (CHC) resin restored endodontically treated mandibular premolars. Settings and Design: Academic, in vitro study. Materials and Methods: The prepared mandibular premolar samples were randomly divided into five groups of 10 each. In Group 1, teeth were left intact. The remaining 40 teeth were endodontically treated and obturated as follows: In Group 2, teeth were obturated with gutta-percha till cementoenamel junction and restored with CHC. Teeth in Groups 3, 4, and 5 were obturated to a depth of 5 mm from the cervical line and restored with dual-cure, nano-hybrid, and short-fiber reinforced composite resins, respectively. Fracture resistance was tested using a universal testing machine. Statistical Analysis Used: One-way analysis of variance and post hoc Tukey's test. Results: Short-fiber reinforced composite resin showed a significantly higher mean fracture resistance value compared with other experimental groups. The mean fracture resistance values were obtained as Group 1 > Group 5 > Group 4 > Group 3 > Group 2. Conclusions: Reinforcement with short-fiber reinforced composite showed significantly higher fracture resistance compared with nano-hybrid and dual-cure composite resins.

9.
Indian J Dent Res ; 33(4): 435-439, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-37006011

RESUMEN

Background: In comparison to multiple file systems, recent advancements in single file retreatment systems had reduced the working time and ease of operation for clinicians. Aim: To compare the efficacy of retreatment systems compared with hand instrumentation, by evaluating their removal efficacy, time required for retreatment and assessment of canal transportation. Methods and Material: Forty premolars were instrumented using ProTaper Gold gold files. Post instrumentation, scan was taken, obturated using warm vertical compaction technique, and stored in artificial saliva for three months and randomly divided into four groups for retreatment. Hand instrumentation (Hi), Neoniti (Nn), Mtwo R (Mt), WaveOne Gold (Wg). Post retreatment, scan was taken. Teeth were sectioned longitudinally and photographed under the stereomicroscope. Retreatment time was recorded, and canal transportation was calculated. Statistical Analysis: The results were analyzed using one-way analysis of variance (ANOVA) followed by Tukey's post hoc test at 95% confidence level. Results: The retreatment time was significantly longer in the Hi group. Within the test groups, a significantly longer time has been taken by Wg (p < 0.05) compared to Mt and Nn. There was no difference in the canal transportation between the single file systems at 3 mm, 6 mm and 9 mm from the apex, there was statistically significant higher transportation for the Hi group at 9 mm from the apex (p < 0.05). Conclusions: All techniques were effective in removal of filling material with minimal canal transportation. Wg system was shown to increased time compared to Nn and Mt systems. Hi group was slowest with maximum canal transportation at 9 mm from the apex.


Asunto(s)
Gutapercha , Materiales de Obturación del Conducto Radicular , Cavidad Pulpar , Retratamiento , Obturación del Conducto Radicular/métodos , Preparación del Conducto Radicular
10.
J Conserv Dent ; 25(1): 88-92, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35722076

RESUMEN

Introduction: Bulk-fill composite restorations displayed substantial annual failure related to imperfect marginal adaptation. Although preheated composites improved, marginal adaptation demonstrated early loss of plasticity. A new technique of ultrasonics plasticization was used for fabricating restorations. Aim: The aim of this study was to assess the clinical behavior of bulk-fill composite resin restorations plasticized by preheating and ultrasonics. Methodology: Randomized split-mouth double-blinded clinical trial was designed. Bulk-fill composite resin (Tetric N-Ceram Bulk Fill Ivoclar Vivadent products, Delhi) was used to fill 56 cavities. In 28 restorations, composite resin was plasticized by preheating in composite warmer (Delta Co., India) and remaining were plasticized with modified ultrasonic-retreatment tip-RT No 2 (Cricdental, India). Clinical follow-up assessments were done at 6 and 12 months using Ryge's criteria. Mann-Whitney U-test was used for statistical analysis with P < 0.05 and effect size of 0.61. Results: Hundred percent clinical success with ultrasonic plasticized group and 95.2% success with preheated composite resin group were observed without statistical significance. Conclusion: The ultrasonics plasticization of composite resin demonstrated comparable results with that of preheated composite resin after 6- and 12-month recall. Use of vibration energy utilizing the thixotropic effect might have resulted in better clinical performance.

11.
Rom J Morphol Embryol ; 51(2): 401-2, 2010.
Artículo en Inglés | MEDLINE | ID: mdl-20495765

RESUMEN

Hepatic, splenic and left gastric arteries are the "classical branches" of celiac trunk. The authors report a rare variation, hepato-spleno-mesenteric trunk with two classical branches of celiac trunk and superior mesenteric artery having common origin from the abdominal aorta. The third classical branch of the celiac trunk (left gastric artery) was directly arising from the abdominal aorta. Knowledge of variations concerning the celiac trunk and superior mesenteric arteries are of great important for both surgical approaches and angiographic examinations.


Asunto(s)
Aorta Abdominal/anomalías , Arteria Hepática/diagnóstico por imagen , Arteria Mesentérica Superior/diagnóstico por imagen , Arteria Esplénica/diagnóstico por imagen , Estómago/irrigación sanguínea , Aorta Abdominal/diagnóstico por imagen , Cadáver , Humanos , Masculino , Persona de Mediana Edad , Radiografía
12.
J Nanosci Nanotechnol ; 9(8): 4910-7, 2009 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-19928168

RESUMEN

Optically clear glasses of various compositions in the system (100-x) TeO2-x(1.5K2O-Li2O-2.5Nb2O5) (2 < or = x < or = 12, in molar ratio) were prepared by the melt-quenching technique. The glassy nature of the as-quenched samples was established via differential scanning calorimetry (DSC). The amorphous and the crystalline nature of the as-quenched and heat-treated samples were confirmed by the X-ray powder diffraction and transmission electron microscopic (TEM) studies. Transparent glasses comprising potassium lithium niobate (K3Li2Nb5O15) microcrystallites on the surface and nanocrystallites within the glass were obtained by controlled heat-treatment of the as-quenched glasses just above the glass transition temperature (T(g)). The optical transmission spectra of these glasses and glass-crystal composites of various compositions were recorded in the 200-2500 nm wavelength range. Various optical parameters such as optical band gap, Urbach energy, refractive index were determined. Second order optical non-linearity was established in the heat-treated samples by employing the Maker-Fringe method.

13.
J Nanosci Nanotechnol ; 9(11): 6549-53, 2009 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-19908563

RESUMEN

We report the synthesis and structural characterization of ferroelectric bismuth vanadate (Bi2VO5.5) (BVO) nanotubes within the nanoporous anodic aluminum oxide (AAO) templates via sol-gel method. The as-prepared BVO nanotubes were characterized by X-ray powder diffraction (XRD), Scanning Electron Microscope (SEM), High-Resolution Transmission Electron Microscope (HRTEM) and the stoichiometry of the nanotubes was established by energy-dispersive X-ray spectroscopy (EDX). Postannealed (675 degrees C for 1 h), BVO nanotubes were a polycrystalline and the XRD studies confirmed the crystal structure to be orthorhombic. The uniformity in diameter and length of the nanotubes as reveled by the TEM and SEM suggested that these were influenced to a guest extent by the thickness and pore diameter of the nanoporous AAO template. EDX analysis demonstrated the formation of stoichiometric Bi2VO5.5 phase. HRTEM confirmed that the obtained BVO nanotubes were made up of nanoparticles of 5-9 nm range. The possible formation mechanism of nanotubes was elucidated.

14.
Indian J Pharmacol ; 51(5): 352-353, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31831927

RESUMEN

Carbamazepine is a commonly used iminostilbene antiepileptic medication and it is estimated that 46.9% of the total antiepileptic drug overdose in the United Kingdom is because of this drug. The overdose of Carbamazepine can show negative effects on multiple systems, these include neurologic (ataxia, seizures, and altered sensorium), cardiac (tachycardia, hypotension) and metabolic manifestations. We reported a case of a 17-year-old girl had an increase in glucose levels after voluntary ingestion carbamazepine tablets. After ingestion, her gross random blood sugar level was increased, then physician suspected that she might be a Type I diabetic,but HbA1C[glycosylated hemoglobin] levels was found normal.Carbamazepine was discontinued and patient received symptomatic therapy. The patient had decreased levels of blood sugar level,after removal of the drug within the next day after ingestion of carbamazepine. A Naranjo assessment was obtained, indicating a definite relationship between the patient's increased in blood glucose levels and her use of carbamazepine.


Asunto(s)
Anticonvulsivantes/envenenamiento , Carbamazepina/envenenamiento , Hiperglucemia/inducido químicamente , Adolescente , Anticonvulsivantes/administración & dosificación , Glucemia/efectos de los fármacos , Carbamazepina/administración & dosificación , Sobredosis de Droga , Femenino , Humanos
15.
Asian Pac J Cancer Prev ; 20(10): 3093-3100, 2019 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-31653159

RESUMEN

AIM: CAPOX treatment in CRC patients was reported to cause several dose-limiting toxicities, and are found responsible for treatment interruption or even discontinuation. Therefore there is a critical need for identifying the predictive biomarkers for such toxicities to prevent them. The aim of our present study is to find the influence of DPYD*9A, DPYD*6 and GSTP1 ile105val gene polymorphisms on CAPOX treatment-associated toxicities in south Indian patients with CRC. PATIENTS AND METHODS: We have recruited 145 newly diagnosed and treatment naive CRC patients in the study. Each Patient received a standard treatment schedule of oxaliplatin 130 mg/m2 infusion over 2 hours on day 1 and oral capecitabine 1000mg/m2 in divided doses twice daily for the next 14 days of a 21-day cycle. 5 ml of the venous blood was collected from each patient and genomic DNA extraction and genotyping. The genotyping analysis of the selected genetic polymorphisms was carried out by real-time PCR using TaqMan SNP genotyping assays obtained from applied biosystems. RESULTS: The major dose-limiting toxicities observed with CAPOX treatment were thrombocytopenia, HFS and PN. DPYD*9A carries were found to be at higher risk for HFS, diarrhoea and thrombocytopenia when compared to patients with wild allele. No significant association was found between DPYD*6, GSTP1 ile105val polymorphisms and CAPOX related toxicities except for thrombocytopenia. CONCLUSION: A significant association was observed between DPYD*9A polymorphism and CAPOX induced dose-limiting toxicities strengthening its role as a predictive biomarker.


Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Neoplasias Colorrectales/tratamiento farmacológico , Dihidrouracilo Deshidrogenasa (NADP)/genética , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Gutatión-S-Transferasa pi/genética , Polimorfismo Genético , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Capecitabina/administración & dosificación , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/patología , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Oxaliplatino/administración & dosificación , Pronóstico
16.
J Nanosci Nanotechnol ; 8(11): 5762-9, 2008 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-19198302

RESUMEN

Nanocrystalline powders of giant dielectric constant material, CaCu3Ti4O12 (CCTO), have been prepared successfully by the molten salt synthesis (MSS) using KCl at 750 degrees C/10 h, which is significantly lower than the calcination temperature (approximately 1000 degrees C) that is employed to obtain phase pure CCTO in the conventional solid-state reaction route. The water washed molten salt synthesized powder, characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) confirmed to be a phase pure CCTO associated with approximately 150 nm sized crystallites of nearly spherical shape. The decrease in the formation temperature/duration of CCTO in MSS method was attributed to an increase in the diffusion rate or a decrease in the diffusion length of reacting ions in the molten salt medium. As a consequence of liquid phase sintering, pellets of as-synthesized KCl containing CCTO powder exhibited higher sinterability and grain size than that of KCl free CCTO samples prepared by both MSS method and conventional solid-state reaction route. The grain size and the dielectric constant of KCl containing CCTO ceramics increased with increasing sintering temperature (900 degrees C-1050 degrees C). Indeed the dielectric constants of these ceramics were higher than that of KCl free CCTO samples prepared by both MSS method and those obtained via the solid-state reaction route and sintered at the same temperature. Internal barrier layer capacitance (IBLC) model was invoked to correlate the observed dielectric constant with the grain size in these samples.


Asunto(s)
Cerámica/química , Cristalización/métodos , Nanoestructuras/química , Nanoestructuras/ultraestructura , Nanotecnología/métodos , Sales (Química)/química , Capacidad Eléctrica , Conductividad Eléctrica , Calor , Sustancias Macromoleculares/química , Ensayo de Materiales , Conformación Molecular , Tamaño de la Partícula , Propiedades de Superficie
17.
Acta Crystallogr C ; 64(Pt 7): o361-3, 2008 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-18599977

RESUMEN

The title salt, C(13)H(12)N(3)(+).H(2)PO(4)(-), contains a nonplanar 2-(2-aminophenyl)-1H-benzimidazol-3-ium cation and two different dihydrogen phosphate anions, both situated on twofold rotation axes in the space group C2. The anions are linked by O-H...O hydrogen bonds into chains of R(2)(2)(8) rings. The anion chains are linked by the cations, via hydrogen-bonding complementarities and electrostatic interactions, giving rise to a sheet structure with alternating rows of organic cations and inorganic anions. Comparison of this structure with that of the pure amine reveals that the two compounds generate characteristically different sheet structures. The anion-anion chain serves as a template for the assembly of the cations, suggesting a possible application in the design of solid-state materials.


Asunto(s)
Enlace de Hidrógeno , Imidazoles/química , Cristalografía , Estructura Molecular
18.
ACS Appl Mater Interfaces ; 10(32): 27278-27286, 2018 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-30048110

RESUMEN

Polymer (poly(vinylidene fluoride) (PVDF)) nanocrystal composites based on lanthanum nickelate (percolative oxide) and barium titanate were fabricated to obtain material systems with a high dielectric constant and low loss to be used for high-charge-storage applications. Lanthanum nickelate (LaNiO3) nanocrystallites were synthesized from a simple citrate-assisted sol-gel route that yielded agglomerated crystallites of an average size of 120 nm. The defective nature of the lanthanum nickelate nanocrystals was revealed by the transmission electron microscopy studies. Hot-pressing method was executed to fabricate the LaNiO3/PVDF nanocrystal composites, and their dielectric characteristics showed a low percolation threshold in the region of fLN (volume fraction of lanthanum nickelate) = 0.10. The percolative conductive filler-polymer nanocrystal composite at the percolation threshold exhibited a dielectric constant (εr) and loss ( D) of 55 and 0.263, respectively, at 10 kHz; the dielectric constant obtained was more than 5 times that of host matrix PVDF. To further improve upon the obtained dielectric properties from the two-phase composites, a high-dielectric-constant material, barium titanate (BaTiO3) nanocrystals, with an average size of 100 nm, was embedded in the polymer matrix as the third phase. The dielectric properties of the three-phase nanocrystal composites were measured as a function of the volume fraction of lanthanum nickelate (which was limited within the percolation threshold), and a dielectric constant as high as 90 and the associated loss of 0.13 at 10 kHz were achieved from fLN = 0.09 and fBT = 0.20. The obtained dielectric constant from this system is 9 times more than that of PVDF and 3 times that of a two-phase barium titanate/PVDF composite, which proves to be a promising material for charge-storage applications.

19.
Eur J Pharm Sci ; 123: 124-134, 2018 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-30048798

RESUMEN

Ritonavir and Lopinavir have previously been demonstrated to decrease the maximum solubility advantage and flux in the presence of each other. The present study investigated the ability of Ritonavir and Lopinavir co-amorphous materials to generate a supersaturated state. Further, it explored the precipitation and flux behavior of co-amorphous materials. The co-amorphous materials of Ritonavir and Lopinavir were prepared by quench cool method and characterized in the solid state using XRPD, DSC, FTIR. The solubility studies were conducted in USP phosphate buffer (pH 6.8) for 12 h. The supersaturation potential and precipitation behavior were studied employing pH shift method. Further, the diffusion behavior was explored in vitro and ex-vivo using a semipermeable membrane and intestinal everted sac method, respectively. The results showed that the co-amorphous materials have the potential to generate a supersaturated state. However, the reduction in the amorphous solubility was observed for both the drug(s) and the degree of reduction was found proportionate with the mole fraction of the compound in the co-amorphous material. Interestingly, the flux of both the drugs from co-amorphous material of 2:1 M ratio (Ritonavir 2: Lopinavir 1) was found exceeding the flux of the individual drugs in the amorphous form. The significant increase in the flux was attributed to the improved drug release properties due to precipitation of drug rich phase of nano/micro dimensions.


Asunto(s)
Composición de Medicamentos , Lopinavir/química , Ritonavir/química , Liberación de Fármacos , Transición de Fase , Solubilidad
20.
J Nanosci Nanotechnol ; 7(3): 1006-13, 2007 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-17450867

RESUMEN

Transparent glasses in the system (100 - x)Li2B4O7 - x(BaO-Bi2O3-Nb2O5) (x = 10, 20, and 30) were fabricated via the conventional melt-quenching technique. The amorphous and glassy characteristics of the as-quenched samples were established by the differential thermal analyses (DTA) and X-ray powder diffraction (XRD) studies. Glass-nanocrystal composites (GNCs) i.e., the glasses embedded with BaBi2Nb2O9 (BBN) nanocrystals (10-50 nm) were produced by heat-treating the as-quenched glasses at temperatures higher than 500 degrees C. Perovskite BBN phase formation through an intermediate fluorite-like phase in the glass matrix was confirmed via XRD and transmission electron microscopic (TEM) studies. The optical transmission properties of these GNCs were found to have a strong compositional (BBN content) dependence. The refractive index (n = 1.90) and optical polarizability (alphao = 15.3 x 10(-24) cm3) of the GNC (x = 30) were larger than those of as-quenched glasses. The temperature dependent dielectric constant (epsilonr) and loss factor (D) for the glasses and GNCs were determined in the 100-40 MHz frequency range. The epsilonr was found to increase with increase in heat-treatment temperatures, while the loss of the glass-nanocomposites was less than that of as-quenched glasses. The sample heat-treated at 620 degrees C/1 h (x = 30) exhibited relaxor behavior associated with a dielectric anomaly in the 150-250 degrees C temperature range. The frequency dependence of the dielectric maximum temperature was found to obey the Vogel-Fulcher relation (Ea = 0.32 eV and Tf = 201 K).


Asunto(s)
Vidrio/química , Nanopartículas del Metal/química , Nanocompuestos/química , Compuestos de Bario/química , Bismuto/química , Boratos/química , Electroquímica , Compuestos de Litio/química , Nanopartículas del Metal/ultraestructura , Microscopía Electrónica , Nanocompuestos/ultraestructura , Nanotecnología , Niobio/química , Óxidos/química , Espectrofotometría , Termodinámica , Difracción de Rayos X
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