Improved manufacturing quality and bonding of laser machined microfluidic systems

Laser micro-machining offers a versatile tool for the rapid manufacturing of polymeric microfluidics systems, with a typical turn-around-time in the order of minutes. However, the chaotic nature of the thermal evaporative ablation process can yield a significant number of defects in the surface of the manufactured microchannels, in the form of residual condensed material. In this work we have investigated the use of solvent evaporation by which to not only laminate bond the laser machined structures but to remove a significant number of the defect formed by the condensation of residual polymer. Results are presented of the surface profiling of the bonded channel structures and demonstrations of the bonding of the microchips to produce autonomous capillary microchannels.

Experimental investigation on bonding properties of reactive liquid rubber epoxy in CFRP retrofitted concretet members

The load bearing capacity of aging reinforced concrete structures, such as bridges, is increasingly extended with the use of Carbon Fibre Reinforced Polymer (CFRP). Premature failure, which is attributed to the rigid behaviour of the bonding agent (epoxy resin) and the high stresses at the interface region, can occur because of the debonding of CFRP sheets from host surfaces. To overcome the debonding issue, the epoxy resin is modified by different reactive liquid polymers to improve its toughness, flexibility, adhesion, and impact resistance. This study reports the usage of two reactive liquid polymers, namely, liquid Carboxyl-Terminated Butadiene-Acrylonitrile (CTBN) and liquid Amine-Terminated Butadiene-Acrylonitrile (ATBN), to improve the mechanical properties of the commercially available MBrace saturant resin when added to a ratio of 100:30 by weight. The neat and modified epoxies were analysed using the Dynamic Mechanical Thermal Analysis (DMTA) to determine and compare the storage modulus and glass transition temperatures of these materials. Moreover, the bonding strength of neat and modified epoxies was evaluated through single-lap shear tests on CFRP sheets bonded to concrete prisms. The results indicate that the modified resins exhibited improved ductility and toughness and became reasonably flexible compared with the neat epoxy resin. The improved properties will help delay the premature debonding failure in CFRP retrofitted concrete members.

The effectiveness of community-based interventions to improve maternal and infant health in the Northeast of Brazil

EMOND, Alan et al. The effectiveness of community-based interventions to improve maternal and infant health in the Northeast of Brazil. Revista Panamericana de Salud Pública/ Pan American Journal of Public Health , v.12, n.2, p.101-110, 2002

Project Pró-Natal: population-based study of perinatal and infant mortality in Natal, Northeast Brazil

RAMOS, Ana Maria de Oliveira et al. Project Pró-Natal: population-based study of perinatal and infant mortality in Natal, Northeast Brazil. Pediatric and Developmental Pathology, v.3, n.1, p.29-35, 2000

Soil texture spatial variability of different parent material in pereira barreto, São Paulo state

The variation of soil textural characteristics is a function of the relief and parent materials. The objective of this work was to study soil texture spatial variability from different parent material in Pereira Barreto, SP. An area of 530.67 hectares was mapped through the use of Global Positioning System receivers and obtaining of Digital Elevation Models. A set of 201 soil samples was collected from every seven hectares, at three depths: 0 - 0.25 m; 0.25 - 0.50 m; and 0.80 - 1.00 m. The amounts of sand, silt and clay were obtained by the pipette method and analyzed by both descriptive statistics and geostatistics. Soil textures varied as a function of parent materials and topography.

Fully Relativistic 4-Components DFT Investigation on Bonding and Dissociation Energy of HgO

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Analysis of biological tissues in infant chest for the development of an equivalent radiographic phantom

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Social support and infant malnutrition: a case-control study in an urban area of Southeastern Brazil

The relationship between malnutrition and social support was first suggested in the mid-1990s. Despite its plausibility, no empirical studies aimed at obtaining evidence of this association could be located. The goal of the present study was to investigate such evidence. A case-control study was carried out including 101 malnourished children (weight-for-age National Center for Health Statistics/WHO 5th percentile) aged 12-23 months, who were compared with 200 well-nourished children with regard to exposure to a series of factors related to their social support system. Univariate and multiple logistic regressions were carried out, odds ratios being adjusted for per capita family income, mother's schooling, and number of children. The presence of an interaction between income and social support variables was also tested. Absence of a partner living with the mother increased risk of malnutrition (odds ratio 2.4 (95 % CI 1.19, 4.89)), even after adjustment for per capita family income, mother's schooling, and number of children. The lack of economic support during adverse situations accounted for a very high risk of malnutrition (odds ratio 10.1 (95 % CI 3.48, 29.13)) among low-income children, but had no effect on children of higher-income families. Results indicate that receiving economic support is an efficient risk modulator for malnutrition among low-income children. In addition, it was shown that the absence of a partner living with the mother is an important risk factor for malnutrition, with an effect independent from per capita family income, mother's schooling, and number of children.

Analysis in vitro of direct bonding system with cyanoacrylate ester and orthodontic wires

The aim of this study was to evaluate the tensile strength of orthodontic wires bonded onto the enamel with cyanoacrylate ester. To obtain the specimens, 120 human premolars (extracted for orthodontic or periodontal reasons) were included in acrylic blocks of rapid polymerization with three teeth each. Four groups were formed with ten specimens each. In the specimens, a dental splint model was made with cyanoacrylate ester and round stainless steel wire. In groups I, II and III, cyanoacrylate ester was used with round steel wires, with variation in diameter: 0.014 inches; 0.016 inches and 0.018 inches, respectively. In group IV, round steel wire 0.018 inches was used with photo polymerizing resin composite with previous acid etching. The adhesive force of the materials was measured in two points under the action of the tensiometer (ETM-USA). The number of loose wires was counted along with those that remained fixed according to the different levels of force applied because of the direction of the tensile force (vertical or horizontal) and the diameter of the wire used. The data obtained were first submitted to a descriptive analysis and then submitted to a statistical analysis (Friedman's Test and Dunn's Test of Multiple Comparison - Epi-info 3.2). Within the limitations of the experimental conditions presented, the cyanoacrylate ester or 'Super Bonder (R)' maintained bonded to enamel and steel wires (0.016 and 0.018 inches) during the tensile strength tests under different levels of applied forces.

Cementation of Prosthetic Restorations: From Conventional Cementation to Dental Bonding Concept

The cementation procedure of metal-free fixed partial dentures exhibits special characteristics about the porcelains and cementation agents, which turns the correct association between these materials necessary. Our purpose in this literature review was to point the main groups of cements associated to metal-free restoration and discuss about the advantages, disadvantages, and recommendations of each one. Our search was confined to the electronic databases PubMed and SciELO and to books about this matter. There are essentially 3 types of hard cement: conventional, resin, or a hybrid of the two. The metal-free restorations can be fixed with conventional or resin cements. The right choice of luting material is of vital importance to the longevity of dental restorative materials. Conventional cements are advantageous when good compressive straight, good film thickness, and water dissolution resistance are necessary. However, they need an ideal preparation, and they are not acid dissolution resistant. Conventional cements are indicated to porcelains that cannot be acid etched. Resin cements represent the choice to metal-free restoration cementation because they present better physical properties and aesthetic than conventional agents.

Infant formula and enamel fluorosis A systematic review

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The influence of time interval between bleaching and enamel bonding

Objectives: the purpose of this study was to investigate the penetration of a conventional adhesive material into enamel bleached with 16% carbamide peroxide and 38% hydrogen peroxide using optical light microscopy.Methods: Extracted human teeth were randomly divided into eight experimental groups with six specimens each, according to the bleaching material and time interval after bleaching and before the bonding procedure. Groups were designated as follows: control group, restorations in unbleached teeth; restorations performed immediately after bleaching; restorations performed 7 days after bleaching; restorations performed 14 days after bleaching; and restorations performed 30 days after bleaching. The length of resin tags was measured with an Axiophot photomicroscope at 400x magnification for the calculation of the proportion of tags of study groups compared to the respective control groups. Analysis of variance was applied for comparison between groups; data were transformed into arcsine (p < 0.05).Results: the specimens of experimental groups, in which restorations were performed 7, 14, and 30 days after bleaching, showed better penetration of adhesive material into enamel than specimens restored immediately after bleaching. There was no statistically significant difference between the bleaching materials employed or in the interaction between bleaching agent and time interval.Conclusions: This suggests that a time interval of at least 7 days should be allowed between enamel bleaching and placement of adhesive bonding agents for accomplishment of composite resin restorations.

The influence of temperature of three adhesive systems on bonding to ground enamel

This study evaluated the microtensile bond strength test (mu T), micromorphology of resin-enamel interface (RET) and etching patterns (EP) promoted by the etch-and-rinse adhesive, Prime&Bond NT (PB), and two self-etching adhesives, Clearfil SE Bond (SE) and Adper Prompt L-Pop (APR), to ground bovine enamel surfaces' when applied at temperatures of 5 degrees C (C), 40 degrees C (H) and 20 degrees C (R). Materials and Methods. Sixty-three bovine incisors were randomly divided into nine experimental groups (n=7) according to adhesive systems and temperatures. The buccal enamel surfaces were flattened with 600-grit SiC paper and abraded with a diamond bur under water-cooling. The adhesive systems were applied according to the manufacturer's instructions. After the restorative procedures, the specimens were sectioned into five slabs. Four slabs were prepared for mu T and one for interface analysis. For etching pattern analysis, the remaining 16 bovine enamel fragments were used (n=2). The adhesives were applied and the surfaces were rinsed with organic solvents after application. The specimens for RET and EP analysis were prepared for SEM analysis. Results. No significant differences among the adhesives were found at R temperature. However, at 5 degrees C, PB and APR presented lower bond strength than SE. At H temperature, higher bond strength was observed for PB than for APR and SE. At C and H temperature, formation of the interdiffusion zone was impaired and the treated enamel surfaces presented an undefined EP.