Optimization of preservative system in ophthalmic suspension with dexamethasone and polymyxin B

A simplex-lattice statistical project was employed to study an optimization method for a preservative system in an ophthalmic suspension of dexametasone and polymyxin B. The assay matrix generated 17 formulas which were differentiated by the preservatives and EDTA (disodium ethylene diamine-tetraacetate), being the independent variable: X-1 = chlorhexidine digluconate (0.010 % w/v); X-2 = phenylethanol (0.500 % w/v); X-3 = EDTA (0.100 % w/v). The dependent variable was the Dvalue obtained from the microbial challenge of the formulas and calculated when the microbial killing process was modeled by an exponential function. The analysis of the dependent variable, performed using the software Design Expert/W, originated cubic equations with terms derived from stepwise adjustment method for the challenging microorganisms: Pseudomonas aeruginosa, Burkholderia cepacia, Staphylococcus aureus, Candida albicans and Aspergillus niger. Besides the mathematical expressions, the response surfaces and the contour graphics were obtained for each assay. The contour graphs obtained were overlaid in order to permit the identification of a region containing the most adequate formulas (graphic strategy), having as representatives: X-1 = 0.10 ( 0.001 % w/v); X-2 = 0.80 (0.400 % w/v); X-3 = 0.10 (0.010 % w/v). Additionally, in order to minimize responses (Dvalue), a numerical strategy corresponding to the use of the desirability function was used, which resulted in the following independent variables combinations: X-1 = 0.25 (0.0025 % w/v); X-2 = 0.75 (0.375 % w/v); X-3 = 0. These formulas, derived from the two strategies (graphic and numerical), were submitted to microbial challenge, and the experimental Dvalue obtained was compared to the theoretical Dvalue calculated from the cubic equation. Both Dvalues were similar to all the assays except that related to Staphylococcus aureus. This microorganism, as well as Pseudomonas aeruginosa, presented intense susceptibility to the formulas independently from the preservative and EDTA concentrations. Both formulas derived from graphic and numerical strategies attained the recommended criteria adopted by the official method. It was concluded that the model proposed allowed the optimization of the formulas in their preservation aspect.

Rheological behavior, zeta potential, and accelerated stability tests of Buriti oil (Mauritia flexuosa) emulsions containing lyotropic liquid crystals

Background: It is well known that the Amazon region presents a huge biodiversity; therefore, countless natural resources are being employed in the production of phytocosmetics and phytomedicines. Objective: The purpose of this work was to obtain emulsions produced with Buriti oil and nonionic surfactants. Methods: Two surfactant systems were employed (Steareth-2 associated to Ceteareth-5 and to Ceteareth-20) to produce the emulsions using phase diagram method. Emulsions were obtained by echo-planar imaging method at 75 degrees C. Rheological behavior and zeta potential were evaluated, and accelerated stability tests were performed. Results: All emulsions analyzed presented pseudoplastic behavior. Zeta potential values were obtained between -14.2 and -53.3 mV. The formulations did not show changes in either physical stability, pH, or rheological behavior after accelerated stability tests. Significant differences were observed only after temperature cycling test. Conclusion: Based on these results, the emulsions obtained could be considered as promising delivery systems.

A spectral clustering algorithm for manufacturing cell formation

A graph clustering algorithm constructs groups of closely related parts and machines separately. After they are matched for the least intercell moves, a refining process runs on the initial cell formation to decrease the number of intercell moves. A simple modification of this main approach can deal with some practical constraints, such as the popular constraint of bounding the maximum number of machines in a cell. Our approach makes a big improvement in the computational time. More importantly, improvement is seen in the number of intercell moves when the computational results were compared with best known solutions from the literature. (C) 2009 Elsevier Ltd. All rights reserved.

Visible and near-infrared luminescent Eu(3+) or Er(3+) doped laponite-derived xerogels and thick films: Structural and spectroscopic properties

Laponite-derived materials represent promising materials for optical applications. In this work, Eu(3+)- or Er(3+)-doped laponite xerogels and films were prepared from colloidal dispersion. Homogeneous, crack-free and transparent single layers were deposited on soda-lime substrates with a thickness of 10 mu m. Structural and spectroscopic properties were analyzed by thermal analyses, X-ray diffractometry, transmission electron microscopy, infrared spectroscopy, and luminescence spectroscopy. The addition of a rare earth ion to the laponite does not promote any changes in thermal stability or phase transition. Laponite clay was identified after annealing up to 500 degrees C, with a decrease in basal spacing when the annealing temperature is changed from 100 degrees C to 500 degrees C. Enstatite polymorphs and amorphous silicate phases were observed after heat treatment at 700 degrees C and 900 degrees C. Stationary and time-dependent luminescence spectra in the visible region for Eu(3+), and (5)D(0) lifetime are discussed in terms of thermal treatment and structural evolution. In the layered host, the Eu(3+) ions are distributed in many different local environments. However, Eu(3+) ions were found to occupy at least two symmetry sites, and the ions are preferentially incorporated into the crystalline enstatite for the materials annealed at 700 degrees C and 900 degrees C. A (5)D(0) lifetime of 1.3 ms and 3.1 ms was obtained for Eu(3+) ions in an amorphous silicate and crystalline MgSiO(3) local environment, respectively. Strong Er(3+) emission at the 1550 nm region was observed for the materials annealed at 900 degrees C, with a bandwidth of 44 nm. (C) 2008 Elsevier B.V. All rights reserved.

Rare Earth Doped SnO(2) Nanoscaled Powders and Coatings: Enhanced Photoluminescence in Water and Waveguiding Properties

Luminescent Eu(3+) and Er(3+) doped SnO(2) powders have been prepared by Sn(4+) hydrolysis followed by a controlled growth reaction using a particle`s surface modifier in order to avoid particles aggregation. The powders so obtained doped with up to 2 mol% rare earth ions are fully redispersable in water at pH > 8 and present the cassiterite structure. Particles size range from 3 to 10 nm as determined by Photon Correlation Spectroscopy. Rare earth ions were found to be essentially incorporated into the cassiterite structure, substituting for Sn(4+), for doping concentration smaller than 0.05 mol%. For higher concentration they are also located at the particles surface. The presence of Eu(3+) ions at the surface of the particles hinder their growth and has therefore allowed the preparation of new materials consisting of water redispersable powders coated with Eu(3+)-beta dike-tonate complexes. Enhanced UV excited photoluminescence was observed in water. SnO(2) single layers with thickness up to 200 nm and multilayer coatings were spin coated on borosilicate glass substrates from the colloidal suspensions. Waveguiding properties were evaluated by the prism coupling technique. For a 0.3 mu m planar waveguide single propagating mode was observed with attenuation coefficient of 3.5 dB/cm at 632.8 nm.

Sol-gel preparation of near-infrared broadband emitting Er(3+)-doped SiO(2)-Ta(2)O(5) nanocomposite films

This article reports a study on the preparation, densification process, and structural and optical properties of SiO(2)-Ta(2)O(5) nanocomposite films obtained by the sol-gel process. The films were doped with Er(3+) and the Si:Ta molar ratio was 90:10. Values of refractive index, thickness and vibrational modes in terms of the number of layers and thermal annealing time are described for the films. The densification process is accompanied by OH group elimination, increase in the refractive index, and changes in film thickness. Full densification of the film is acquired after 90 min of annealing at 900 degrees C. The onset of crystallization and devitrification, with the growth of Ta(2)O(5) nanocrystals occurs with film densification, evidenced by high-resolution transmission electron microscopy. The Er(3+)-doped nanocomposite annealed at 900 degrees C consists of Ta(2)O(5) nanoparticles, with sizes around 2 nm, dispersed in the SiO(2) amorphous phase. The main emission peak of the film is detected at around 1532 nm, which can be assigned to the (4)I(13/2)->(4)I(15/2) transition of the Er(3+) ions present in the nanocomposites. This band has a full width at half medium of 64 nm, and the lifetime measured for the (4)I(13/2) levels is 5.4 ms, which is broader compared to those of other silicate systems. In conclusion, the films obtained in this work are excellent candidates for use as active planar waveguide. (C) 2010 Elsevier B.V. All rights reserved.

Er(3+)-doped silica-hafnia films for optical waveguides and spherical resonators

In this paper we present some result on sol-gel derived silica-hafnia systems. In particular we focus on fabrication, morphological and spectroscopic assessment of Er(3+)-activated thin films. Two examples of silica-hafnia-derived waveguiding glass ceramics, prepared by top-down and bottom-up techniques are reported, and the main optical properties are discussed. Finally, some properties of activated microspherical resonators, having a silica core, obtained by melting the end of a telecom fiber, coated with an Er(3+)-doped 70SiO(2)-30HfO(2) film, are presented. (C) 2009 Elsevier B.V. All rights reserved.

Adsorption of cholate anions on layered double hydroxides: effects of temperature, ionic strength and pH

Layered Double Hydroxides are a class of materials that can be described as positively charged planar layers consisting of divalent and trivalent cations in the center of edge-sharing octahedra. The positive charge in the LDH layers must be compensated by anion intercalation. These materials have applications that include adsorption and/or sorption of anionic species. Cholic acid is one of the main acids produced by the liver. It promotes transport of lipids through aqueous systems. This work reports on the adsorption of Cholic acid anions in MgAl-CO3-LDH taking ionic strength, pH, and temperature effects into account. The adsorbent was characterized by different techniques. Cholate anion adsorption was performed at two different temperatures (298 and 323 K), two different ionic strength conditions (0.0 and 0.1 M of NaCl), and two different pH values (7.0 and 10.0). The results show that the sorption of Cholate anions in calcined LDH can remove a considerable amount of these anions from the medium. Cholate anion adsorption in the LDH with no calcining also occurs, but at a lower amount.

Characterization of high density lipoprotein particles in familial apolipoprotein A-I deficiency

Our aim was to characterize HDL subspecies and fat-soluble vitamin levels in a kindred with familial apolipoprotein A-I (apoA-I) deficiency. Sequencing of the APOA1 gene revealed a nonsense mutation at codon 22, Q[22] X, with two documented homozygotes, eight heterozygotes, and two normal subjects in the kindred. Homozygotes presented markedly decreased HDL cholesterol levels, undetectable plasma apoA-1, tuboeruptive and planar xanthomas, mild corneal arcus and opacification, and severe premature coronary artery disease. In both homozygotes, analysis of HDL particles by two-dimensional gel electrophoresis revealed undetectable apoA-I, decreased amounts of small a-3 migrating apoA-II particles, and only modestly decreased normal amounts of slow a migrating apoA-IV- and apoE-containing HDL, while in the eight heterozygotes, there was loss of large alpha-1 HDL particles. There were no significant decreases in plasma fat-soluble vitamin levels noted in either homozygotes or heterozygotes compared with normal control subjects. Our data indicate that isolated apoA-I deficiency results in marked HDL deficiency with very low apoA-II alpha-3 HDL particles, modest reductions in the separate and distinct plasma apoA-IV and apoE HDL particles, tuboeruptive xanthomas, premature coronary atherosclerosis, and no evidence of fat malabsorption.

IMAGE QUANTIFICATION FOR RADIATION DOSE CALCULATIONS-LIMITATIONS AND UNCERTAINTIES

Radiation dose calculations in nuclear medicine depend on quantification of activity via planar and/or tomographic imaging methods. However, both methods have inherent limitations, and the accuracy of activity estimates varies with object size, background levels, and other variables. The goal of this study was to evaluate the limitations of quantitative imaging with planar and single photon emission computed tomography (SPECT) approaches, with a focus on activity quantification for use in calculating absorbed dose estimates for normal organs and tumors. To do this we studied a series of phantoms of varying complexity of geometry, with three radionuclides whose decay schemes varied from simple to complex. Four aqueous concentrations of (99m)Tc, (131)I, and (111)In (74, 185, 370, and 740 kBq mL(-1)) were placed in spheres of four different sizes in a water-filled phantom, with three different levels of activity in the surrounding water. Planar and SPECT images of the phantoms were obtained on a modern SPECT/computed tomography (CT) system. These radionuclides and concentration/background studies were repeated using a cardiac phantom and a modified torso phantom with liver and ""tumor"" regions containing the radionuclide concentrations and with the same varying background levels. Planar quantification was performed using the geometric mean approach, with attenuation correction (AC), and with and without scatter corrections (SC and NSC). SPECT images were reconstructed using attenuation maps (AM) for AC; scatter windows were used to perform SC during image reconstruction. For spherical sources with corrected data, good accuracy was observed (generally within +/- 10% of known values) for the largest sphere (11.5 mL) and for both planar and SPECT methods with (99m)Tc and (131)I, but were poorest and deviated from known values for smaller objects, most notably for (111)In. SPECT quantification was affected by the partial volume effect in smaller objects and generally showed larger errors than the planar results in these cases for all radionuclides. For the cardiac phantom, results were the most accurate of all of the experiments for all radionuclides. Background subtraction was an important factor influencing these results. The contribution of scattered photons was important in quantification with (131)I; if scatter was not accounted for, activity tended to be overestimated using planar quantification methods. For the torso phantom experiments, results show a clear underestimation of activity when compared to previous experiment with spherical sources for all radionuclides. Despite some variations that were observed as the level of background increased, the SPECT results were more consistent across different activity concentrations. Planar or SPECT quantification on state-of-the-art gamma cameras with appropriate quantitative processing can provide accuracies of better than 10% for large objects and modest target-to-background concentrations; however when smaller objects are used, in the presence of higher background, and for nuclides with more complex decay schemes, SPECT quantification methods generally produce better results. Health Phys. 99(5):688-701; 2010

Reference distribution of the bioelectrical impedance vector in healthy term newborns

Bioelectrical impedance vector analysis (BIVA) is a new method that is used for the routine monitoring of the variation in body fluids and nutritional status with assumptions regarding body composition values. The aim of the present study was to determine bivariate tolerance intervals of the whole-body impedance vector and to describe phase angle (PA) values for healthy term newborns aged 7-28 d. This descriptive cross-sectional study was conducted on healthy term neonates born at a low-risk public maternity. General and anthropometric neonatal data and bioelectrical impedance data (800 mu A-50 kHz) were obtained. Bivariate vector analysis was conducted with the resistance-reactance (RXc) graph method. The BIVA software was used to construct the graphs. The study was conducted on 109 neonates (52.3% females) who were born at term, adequate for gestational age, exclusively breast-fed and aged 13 (SD 3.6) d. We constructed one standard, reference, RXc-score graph and RXc-tolerance ellipses (50, 75 and 95 %) that can be used with any analyser. Mean PA was 3.14 (SD 0.43)degrees (3.12 (SD 0.39)degrees for males and 3.17 (SD 0.48)degrees for females). Considering the overlapping of ellipses of males and females with the general distribution, a graph for newborns aged 7-28 d with the same reference tolerance ellipse was defined for boys and girls. The results differ from those reported in the literature probably, in part, due to the ethnic differences in body composition. BIVA and PA permit an assessment without the need to know body weight and the prediction error of conventional impedance formulas.

Finite-Element Analysis of Stress on Dental Implant Prosthesis

Background: Understanding how clinical variables affect stress distribution facilitates optimal prosthesis design and fabrication and may lead to a decrease in mechanical failures as well as improve implant longevity. Purpose: In this study, the many clinical variations present in implant-supported prosthesis were analyzed by 3-D finite element method. Materials and Method: A geometrical model representing the anterior segment of a human mandible treated with 5 implants supporting a framework was created to perform the tests. The variables introduced in the computer model were cantilever length, elastic modulus of cancellous bone, abutment length, implant length, and framework alloy (AgPd or CoCr). The computer was programmed with physical properties of the materials as derived from the literature, and a 100N vertical load was used to simulate the occlusal force. Images with the fringes of stress were obtained and the maximum stress at each site was plotted in graphs for comparison. Results: Stresses clustered at the elements closest to the loading point. Stress increase was found to be proportional to the increase in cantilever length and inversely proportional to the increase in the elastic modulus of cancellous bone. Increasing the abutment length resulted in a decrease of stress on implants and framework. Stress decrease could not be demonstrated with implants longer than 13 mm. A stiffer framework may allow better stress distribution. Conclusion: The relative physical properties of the many materials involved in an implant-supported prosthesis system affect the way stresses are distributed.