Thin titanium oxide films deposited by e-beam evaporation with additional rapid thermal oxidation and annealing for ISFET applications

Titanium oxide (TiO(2)) has been extensively applied in the medical area due to its proved biocompatibility with human cells [1]. This work presents the characterization of titanium oxide thin films as a potential dielectric to be applied in ion sensitive field-effect transistors. The films were obtained by rapid thermal oxidation and annealing (at 300, 600, 960 and 1200 degrees C) of thin titanium films of different thicknesses (5 nm, 10 nm and 20 nm) deposited by e-beam evaporation on silicon wafers. These films were analyzed as-deposited and after annealing in forming gas for 25 min by Ellipsometry, Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy (RAMAN), Atomic Force Microscopy (AFM), Rutherford Backscattering Spectroscopy (RBS) and Ti-K edge X-ray Absorption Near Edge Structure (XANES). Thin film thickness, roughness, surface grain sizes, refractive indexes and oxygen concentration depend on the oxidation and annealing temperature. Structural characterization showed mainly presence of the crystalline rutile phase, however, other oxides such Ti(2)O(3), an interfacial SiO(2) layer between the dielectric and the substrate and the anatase crystalline phase of TiO(2) films were also identified. Electrical characteristics were obtained by means of I-V and C-V measured curves of Al/Si/TiO(x)/Al capacitors. These curves showed that the films had high dielectric constants between 12 and 33, interface charge density of about 10(10)/cm(2) and leakage current density between 1 and 10(-4) A/cm(2). Field-effect transistors were fabricated in order to analyze I(D) x V(DS) and log I(D) x Bias curves. Early voltage value of -1629 V, R(OUT) value of 215 M Omega and slope of 100 mV/dec were determined for the 20 nm TiO(x) film thermally treated at 960 degrees C. (C) 2009 Elsevier B.V. All rights reserved.

Junctionless Multiple-Gate Transistors for Analog Applications

This paper presents the evaluation of the analog properties of nMOS junctionless (JL) multigate transistors, comparing their performance with those exhibited by inversion-mode (IM) trigate devices of similar dimensions. The study has been performed for devices operating in saturation as single-transistor amplifiers, and we have considered the dependence of the analog properties on fin width W(fin) and temperature T. Furthermore, this paper aims at providing a physical insight into the analog parameters of JL transistors. For that, in addition to device characterization, 3-D device simulations were performed. It is shown that, depending on gate voltage, JL devices can present both larger Early voltage V(EA) and larger intrinsic voltage gain A(V) than IM devices of similar dimensions. In addition, V(EA) and A(V) are always improved in JL devices when the temperature is increased, whereas they present a maximum value around room temperature for IM transistors.

Harmonic distortion analysis of double gate graded-channel MOSFETs operating in saturation

In this work we present an analysis of harmonic distortion (HD) in graded-channel (GC) gate-all-a round (GAA) devices operating in saturation region for analog applications. The study has been performed through device characterization and two-dimensional process and device simulations. The overall study has been done on the total and third order HDs. When applied in the saturation regime as an amplifier, the GC outperforms conventional GAA transistors presenting simultaneously higher transconductance, lower drain output conductance and more than 15 dB improved linearity. The influence of channel length reduction on the H D is also analyzed. Although slight linearity degradation is observed in both the conventional and the GC devices when reducing the channel length, the HD presented by the GC transistor is significantly lower than the one showed by conventional device for any Studied channel length. This allows AC input signal amplitude up to 20 times higher than the conventional GAA for a same specified distortion level. (C) 2008 Elsevier Ltd. All rights reserved.

Gastro-resistant Pellets of Didanosine obtained by Extrusion and Spheronization: Assessing the Production Process

The aim this work was develop gastro-resistant pellets of didanosine as well as study the impact on the pellets properties, regarding the way as the binder was added and drying process used. The pellets formation was accompanied by analysis of morphological parameters and didanosine dissolution. In the most cases, pellets showed diameter around 1.0 mm and shape parameters acceptable. The variations of the process did not interfere significantly in pellets size. In turn, drying in fluid bed favored the dissolution of didanosine, in contrast to binder addition on powder form that impaired. In another hand, this last resulted in the best aspect factor (about 1.1). Gastro-resistant pellets showed adequate dissolution, compatible with this type of dosage form. The variables of process studied enabled obtain pellets with characteristics of shape and dissolution just slightly different, indicating flexibility of the formulation for production of gastro-resistant pellets of didanosine.

The Preparation of Ternary Solid Dispersions of an Herbal Drug via Spray Drying of Liquid Feed

The present study aimed the preparation and characterization of ternary solid dispersions by direct spray drying of a liquid suspension containing curcumin, a solubility enhancer and a drying aid. The experiments followed a Box-Behnken design in order to evaluate the influence of temperature, ratio of curcumin: lipidic carrier, and the collodial silicon dioxide content on the characteristics of the microparticulated solid dispersions. The angle of repose, Hausner factor, Carr index, water activity, and solubility were used to characterize solid dispersions. The results show that water activity, Hausner factor, and Carr index varied in an acceptable range for pharmaceutical purposes. The condition that maximizes solubility was determined using an exploratory design based on a surface response analysis and allowed a 3200-fold increase in curcumin solubility. Ternary solid dispersion showed a 90% curcumin release after 10min during a dissolution test. The results show that the spray drying of a liquid feed is an attractive and promising alternative to obtain enhanced solubility drug ternary solid dispersions.

DRYING OF HERBAL EXTRACT IN A DRAFT-TUBE SPOUTED BED

This work evaluates the feasibility of the draft-tube spouted bed for drying of herbal extract. Drying runs were carried out according to a central composite design in a conical-cylindrical draft-tube spouted bed. The variables studied were the percentage of the drying aid (ADJ), the drying gas flow rate relative to gas flow at minimum spouting (Q/Q(ms)), and the flow rate of extract fed to the system relative to the spouting gas flow rate W(s)/W(g)). Colloidal silicon dioxide was the drying aid used in order to improve drying performance. Statistical analysis of the effects of processing parameters on product recovery, product accumulation in the bed, and product properties permitted the identification of parameters presenting significant effects on drying. Optimized drying conditions were related to experimental parameters as follow: high levels of the percentage of drying adjuvant (ADJ), high airflow rate relative to minimum spouting (Q/Q(ms)), and low values of the feed flow rate of the extract relative to the gas flow rate (W(s)/W(g)).

Preparation, characterization and in vitro cytotoxicity of BSA-based nanospheres containing nanosized magnetic particles and/or photosensitizer

This study reports on the preparation, characterization and in vitro toxicity test of a new nano-drug delivery system (NDDS) based on bovine serum albumin (BSA) nanospheres which incorporates surface-functionalized magnetic nanoparticles (MNP) and/or the silicon(IV) phthalocyanine (NzPc). The new NDDS was engineered for use in photodynamic therapy (PDT) combined with hyperthermia (HPT) to address cancer treatment. The BSA-based nanospheres, hosting NzPc, MNP or both (NzPc and MNP), present spherical shape with hydrodynamic average diameter values ranging from 170 to 450 nm and zeta potential of around -23 mV. No difference on the fluorescence spectrum of the encapsulated NzPc was found regardless of the presence of MNP. Time-dependent fluorescence measurements of the encapsulated NzPc revealed a bi-exponential decay for samples incorporating only NzPc and NzPc plus MNP, in the time window ranging from 1.70 to 5.20 ns. The in vitro assay, using human fibroblasts, revealed no cytotoxic effect in all samples investigated, demonstrating the potential of the tested system as a synergistic NDDS. (C) 2009 Elsevier B.V. All rights reserved.

Effect of a highly concentrated lipopeptide extract of Bacillus subtilis on fungal and bacterial cells

Lipopeptides produced by Bacillus subtilis are known for their high antifungal activity. The aim of this paper is to show that at high concentration they can damage the surface ultra-structure of bacterial cells. A lipopeptide extract containing iturin and surfactin (5 mg mL-1) was prepared after isolation from B. subtilis (strain OG) by solid phase extraction. Analysis by atomic force microscope (AFM) showed that upon evaporation, lipopeptides form large aggregates (0.1-0.2 mu m2) on the substrates silicon and mica. When the same solution is incubated with fungi and bacteria and the system is allowed to evaporate, dramatic changes are observed on the cells. AFM micrographs show disintegration of the hyphae of Phomopsis phaseoli and the cell walls of Xanthomonas campestris and X. axonopodis. Collapses to fungal and bacterial cells may be a result of formation of pores triggered by micelles and lamellar structures, which are formed above the critical micelar concentration of lipopeptides. As observed for P. phaseoli, the process involves binding, solubilization, and formation of novel structures in which cell wall components are solubilized within lipopeptide vesicles. This is the first report presenting evidences that vesicles of uncharged and negatively charged lipopeptides can alter the morphology of gram-negative bacteria.

Er(3+) doped phosphoniobate glasses and planar waveguides: structural and optical properties

Phosphoniobate glasses with composition (mol%) (100-x) NaPO(3)-xNb(2)O(5) ( x varying from 11 to 33) were prepared and characterized by means of thermal analysis, Fourier transform infrared spectroscopy, Raman scattering and (31)P nuclear magnetic resonance. The addition of Nb(2)O(5) to the polyphosphate base glass leads to depolymerization of the metaphosphate structure. Different colors were observed and assigned as indicating the presence of Nb(4+) ions, as confirmed by electron paramagnetic resonance measurements. The color was observed to depend on the glass composition and melting temperature as well. Er(3+) containing samples were also prepared. Strong emission in the 1550 nm region was observed. The Er(3+4)I(15/2) emission quantum efficiency was observed to be 90% and the quenching concentration was observed to be 1.1 mol%( 1.45 x 10(20) ions cm(-3)). Planar waveguides were prepared by Na(+)-K(+)-Ag(+) ion exchange with Er(3+) containing samples. Optical parameters of the waveguides were measured at 632.8, 543.5 and 1550 nm by the prism coupling technique as a function of the ion exchange time and Ag(+) concentration. The optimized planar waveguides show a diffusion depth of 5.9 mu m and one propagating mode at 1550 nm.

Preparation, characterization and catalytic studies of V2O5-SiO2 xerogel composite

In this work, we report the synthesis, characterization and catalytic properties of a vanadium oxide-silicon oxide composite xerogel prepared by a soft chemistry approach. In order to obtain such material, we submitted a vanadium pentoxide gel previously synthesized via protonation of metavanadate species to an ""in situ"" progressive polycondensation into silica gel. The material has been characterized by X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. Further, the catalytic activity of this material was evaluated for the epoxidation of styrene and cyclooctene using iodosylbenzene, hydrogen peroxide and m-chloroperbenzoic acid as the oxidizing agent.

Effect of Diode-Laser and AC Magnetic Field of Bovine Serum Albumin Nanospheres Loaded with Phthalocyanine and Magnetic Particles

This study reports on the development and characterization of bovine serum albumin (BSA) nanospheres containing Silicon(IV) phthalocyanine (NzPc) and/or maghemite nanoparticles (MNP), the latter introduced via ionic magnetic fluid (MF). The nanosized BSA-loaded samples were designed for synergic application while combining Photodynamic Therapy and Hyperthermia. Incorporation of MNP in the albumin-based template, allowing full control of the magnetic content, was accomplished by adding a highly-stable ionic magnetic fluid sample to the albumin suspension, following heat denaturing. The material`s evaluation was performed using Zeta potential measurements and scanning electron microscopy. The samples were characterized by steady-state techniques and time-resolved fluorescence. The in vitro assay, using human fibroblasts, revealed no cytotoxic effect in all samples investigated, demonstrating the potential of the tested system as a synergistic drug delivery system.

In vivo electrochemical characterization and inflammatory response of multiwalled carbon nanotube-based electrodes in rat hippocampus

Stimulating neural electrodes are required to deliver charge to an environment that presents itself as hostile. The electrodes need to maintain their electrical characteristics (charge and impedance) in vivo for a proper functioning of neural prostheses. Here we design implantable multi-walled carbon nanotubes coating for stainless steel substrate electrodes, targeted at wide frequency stimulation of deep brain structures. In well-controlled, low-frequency stimulation acute experiments, we show that multi-walled carbon nanotube electrodes maintain their charge storage capacity (CSC) and impedance in vivo. The difference in average CSCs (n = 4) between the in vivo (1.111 mC cm(-2)) and in vitro (1.008 mC cm(-2)) model was statistically insignificant (p > 0.05 or P-value = 0.715, two tailed). We also report on the transcription levels of the pro-inflammatory cytokine IL-1 beta and TLR2 receptor as an immediate response to low-frequency stimulation using RT-PCR. We show here that the IL-1 beta is part of the inflammatory response to low-frequency stimulation, but TLR2 is not significantly increased in stimulated tissue when compared to controls. The early stages of neuroinflammation due to mechanical and electrical trauma induced by implants can be better understood by detection of pro-inflammatory molecules rather than by histological studies. Tracking of such quantitative response profits from better analysis methods over several temporal and spatial scales. Our results concerning the evaluation of such inflammatory molecules revealed that transcripts for the cytokine IL-1 beta are upregulated in response to low-frequency stimulation, whereas no modulation was observed for TLR2. This result indicates that the early response of the brain to mechanical trauma and low-frequency stimulation activates the IL-1 beta signaling cascade but not that of TLR2.

Hemodynamic effects of inducible nitric oxide synthase inhibition combined with sildenafil during acute pulmonary embolism

While endogenous nitric oxide (NO) may be relevant to the beneficial hemodynamic effects produced by sildenafil during acute pulmonary embolism (APE), huge amounts of inducible NO synthase (iNOS)derived NO may contribute to lung injury. We hypothesized that iNOS inhibition with S-methylisothiourea could attenuate APE-induced increases in oxidative stress and pulmonary hypertension and, therefore, could improve the beneficial hemodynamic and antioxidant effects produced by sildenafil during APE. Hemodynamic evaluations were performed in non-embolized dogs treated with saline (n = 4), S-methylisothiourea (0.01 mg/kg followed by 0.5 mg/kg/h, n = 4), sildenafil (0.3 mg/kg, n = 4), or S-methylisothiourea followed by sildenafil (n = 4), and in dogs that received the same drugs and were embolized with silicon microspheres (n = 8 for each group). Plasma nitrite/nitrate (NOx) and thiobarbituric acid reactive substances (TBARS) concentrations were determined by Griess and a fluorometric assay, respectively. APE increased mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance index (PVRI) by 25 +/- 1.7 mm Hg and by 941 +/- 34 dyn s cm(-5) m(-2), respectively. S-methylisothiourea neither attenuated APE-induced pulmonary hypertension, nor enhanced the beneficial hemodynamic effects produced by sildenafil after APE (>50% reduction in pulmonary vascular resistance). While sildenafil produced no change in plasma NOx concentrations, S-methylisothiourea alone or combined with sildenafil blunted APE-induced increases in NOx concentrations. Both drugs, either alone or combined, produced antioxidant effects. In conclusion, although iNOS-derived NO may play a key role in APE-induced oxidative stress, our results suggest that the iNOS inhibitor S-methylisothiourea neither attenuates APE-induced pulmonary hypertension, nor enhances the beneficial hemodynamic effects produced by sildenafil. (C) 2010 Elsevier Inc. All rights reserved.

Prevention of toothbrushing abrasion of acid-softened enamel by CO(2) laser irradiation

Objective: The aim of the present study was to evaluate the effect of CO(2) laser irradiation (10.6 mu m) at 0.3 J/cm(2) (0.5 mu s; 226 Hz) on the resistance of softened enamel to toothbrushing abrasion, in vitro. Methods: Sixty human enamel samples were obtained, polished with silicon carbide papers and randomly divided into five groups (n = 12), receiving 5 different surface treatments: laser irradiation (L), fluoride (AmF/NaF gel) application (F), laser prior to fluoride (LF), fluoride prior to laser (FL), non-treated control (C). After surface treatment they were submitted to a 25-day erosive-abrasive cycle in 100 ml sprite light (90 s) and brushed twice daily with an electric toothbrush. Between the demineralization periods samples were immersed in supersaturated mineral solution. At the end of the experiments enamel surface loss was determined using a contact profilometer and morphological analysis was performed using scanning electron microscopy (SEM). For SEM analysis of demineralization pattern, cross-sectional cuts of cycled samples were prepared. The data were statistically analysed by one-way ANOVA model with subsequent pairwise comparison of treatments. Results: Abrasive surface loss was significantly lower in all laser groups compared to both control and fluoride groups (p < 0.0001 in all cases). Amongst the laser groups no significant difference was observed. Softened enamel layer underneath lesions was less pronounced in laser-irradiated samples. Conclusion: Irradiation of dental enamel with a CO(2) laser at 0.3 J/cm(2) (5 mu s, 226 Hz) either alone or in combination with amine fluoride gel significantly decreases toothbrushing abrasion of softened-enamel, in vitro. (C) 2011 Elsevier Ltd. All rights reserved.

Rehardening of acid-softened enamel and prevention of enamel softening through CO(2) laser irradiation

Objectives: The aims of the present study were to investigate whether irradiation with a CO(2) laser could prevent surface softening (i) in sound and (ii) in already softened enamel in vitro. Methods: 130 human enamel samples were obtained and polished with silicon carbide papers. They were divided into 10 groups (n = 13) receiving 5 different surface treatments: laser irradiation (L), fluoride (AmF/NaF gel) application (F), laser prior to fluoride (LF), fluoride prior to laser (FL), non-treated control (C); and submitted to 2 different procedures: half of the groups was acid-softened before surface treatment and the other half after. Immersion in 1% citric acid was the acid challenge. Surface microhardness (SMH) was measured at baseline, after softening and after treatment. Additionally, fluoride uptake in the enamel was quantified. The data were statistically analysed by two-way repeated measurements ANOVA and post hoc comparisons at 5% significance level. Results: When softening was performed either before or after laser treatment, the L group presented at the end of the experiments SMH means that were not significantly different from baseline (p = 0.8432, p = 0.4620). Treatment after softening resulted for all laser groups in statistically significant increase in SMH means as compared to values after softening (p < 0.0001). Enamel fluoride uptake was significantly higher for combined laser-fluoride treatment than in control (p < 0.0001). Conclusion: Irradiation of dental enamel with a CO(2) laser at 0.3J/cm(2) (5 mu s, 226 Hz) not only significantly decreased erosive mineral loss (97%) but also rehardened previously softened enamel in vitro. (C) 2011 Elsevier Ltd. All rights reserved.