The influence of some parameters on the surface roughness of thin copper foils using statistical analysis

The influence of nucleation potential, nucleation time, growth potential and substrate roughness on the surface roughness of thin copper foils deposited electrolytically on titanium substrates from a 83 g dm^–3 Cu²⁺ and 140 g dm^–3 H₂SO₄ solution at a temperature of 65 °C, using 2k⁴ factorial design, was studied. A mathematical model to determine the average surface roughness, a quality parameter of thin copper foils, was established. Statistical adjustment of the model enables its use in accurate prediction (error lower than 5%) of the average surface roughness of thin copper foils. The initial steps of copper nucleation and growth are particularly important for the quality of thin (18 m) copper foils, because during its manufacture, a rapid and homogeneous covering of the entire surface of the electrode becomes fundamental in order to obtain foils with a low surface roughness and a low degree of pinholes per unit area. Mechanisms for copper nucleation on titanium, based on the Thirsk and Harrison model for different experimental conditions, were determined with the aid of potentiostatic current transients. It was shown that the roughness of the thin copper foils is a function of not only the growth process, but also the nucleation process and that the lowest surface roughness is related to a pre-nucleation step at –0.590 V for 10 ms on a titanium substrate polished with 600-grit paper.     

Electrospun poly(ε-caprolactone) matrices containing silver sulfadiazine complexed with β-cyclodextrin as a new pharmaceutical dosage form to wound healing: preliminary physicochemical and biological evaluation

Cooperation between researchers in the areas of medical, pharmaceutical and materials science has facilitated the development of pharmaceutical dosage forms that elicit therapeutic effects and protective action with a single product. In addition to optimizing pharmacologic action, such dosage forms provide greater patient comfort and increase success and treatment compliance. In the present work, we prepared semipermeable bioactive electrospun fibers for use as wound dressings containing silver sulfadiazine complexed with β-cyclodextrin in a poly(?-caprolactone) nanofiber matrix aiming to reduce the direct contact between silver and skin and to modulate the drug release. Wound dressings were prepared by electrospinning, and were subjected to ATR-FT-IR and TG/DTG assays to evaluate drug stability. The hydrophilicity of the fibrous nanostructure in water and PBS buffer was studied by goniometry. Electrospun fibers permeability and swelling capacity were assessed, and a dissolution test was performed. In vitro biological tests were realized to investigate the biological compatibility and antimicrobial activity. We obtained flexible matrices that were each approximately 1.0?g in weight. The electrospun fibers were shown to be semipermeable, with water vapor transmission and swelling indexes compatible with the proposed objective. The hydrophilicity was moderate. Matrices containing pure drug modulated drug release adequately during 24?h but presented a high hemolytic index. Complexation promoted a decrease in the hemolytic index and in the drug release but did not negatively impact antimicrobial activity. The drug was released predominantly by diffusion. These results indicate that electrospun PCL matrices containing β-cyclodextrin/silver sulfadiazine inclusion complexes are a promising pharmaceutical dosage form for wound healing.     

Efficacy of in-office bleaching techniques combined with the application of a casein phosphopeptide-amorphous calcium phosphate paste at different moments and its influence on enamel surface properties

OBJECTIVES: The aim of this in vitro study was to investigate the efficacy of in‐office bleaching technique combined with the application of a casein phosphopeptide‐amorphous calcium phosphate (CPP‐ACP) paste (MI Paste–MI) at different moments and its influence on enamel surface properties. METHODS: Eighty bovine dental crowns were randomly allocated into eight groups (n = 10), and bleached with either 35% hydrogen peroxide (HP) or 37% carbamide peroxide (CP). Four different protocols of application of MI were considered: without MI, MI applied before bleaching, MI applied after bleaching, and MI applied both before and after bleaching. Bleaching effectiveness was measured by the VITA EasyShade spectrophotometer utilizing the CIEL*a*b* system (ΔE, ΔL*, Δa*, and Δb*). Color readings were measured at baseline, 7, 14, and 21 days. Hardness and roughness were measured at baseline (T0) and immediately after bleaching (T14). Data were subjected to the two‐way ANOVA for repeated measurements and Tukey's test at 5%. RESULTS: HP groups achieved the greatest color change. The application of a CPP‐ACP paste did not reduce the efficacy of bleaching peroxides. Samples bleached with CP showed decreased hardness at T14. Samples bleached with HP that received the application of MI before and before/after bleaching did not present hardness decrease at T14. Samples bleached with peroxides only and received MI after bleaching showed increased roughness at T14. CONCLUSIONS: The use of CPP‐ACP was able to prevent negative changes in roughness and hardness of bovine enamel when associated to hydrogen peroxide, and might be applied before/after the bleaching protocol. Microsc. Res. Tech. 75:1019–1025, 2012. © 2012 Wiley Periodicals, Inc.     

The SB-index and the HSB-index: efficient indices for spatial data warehouses

Spatial data warehouses (SDWs) allow for spatial analysis together with analytical multidimensional queries over huge volumes of data. The challenge is to retrieve data related to ad hoc spatial query windows according to spatial predicates, avoiding the high cost of joining large tables. Therefore, mechanisms to provide efficient query processing over SDWs are essential. In this paper, we propose two efficient indices for SDW: the SB-index and the HSB-index. The proposed indices share the following characteristics. They enable multidimensional queries with spatial predicate for SDW and also support predefined spatial hierarchies. Furthermore, they compute the spatial predicate and transform it into a conventional one, which can be evaluated together with other conventional predicates by accessing a star-join Bitmap index. While the SB-index has a sequential data structure, the HSB-index uses a hierarchical data structure to enable spatial objects clustering and a specialized buffer-pool to decrease the number of disk accesses. The advantages of the SB-index and the HSB-index over the DBMS resources for SDW indexing (i.e. star-join computation and materialized views) were investigated through performance tests, which issued roll-up operations extended with containment and intersection range queries. The performance results showed that improvements ranged from 68% up to 99% over both the star-join computation and the materialized view. Furthermore, the proposed indices proved to be very compact, adding only less than 1% to the storage requirements. Therefore, both the SB-index and the HSB-index are excellent choices for SDW indexing. Choosing between the SB-index and the HSB-index mainly depends on the query selectivity of spatial predicates. While low query selectivity benefits the HSB-index, the SB-index provides better performance for higher query selectivity.     

Adaptation of the plasma process with automatic wire feeding for recovery of surfaces by automated welding

Damaged surfaces are normally recovered by means of processes of welding; they normally have complex geometries and are located in positions that are unfavourable for welding. Automated welding is the natural alternative as it presents advantages when compared with the manual process, such as reductions in the time and total cost of the recovery, better control of the geometry of the recovered surface, better uniformity and welding quality. Automated welding using the plasma process with automatic wire feed, although it provides excellent geometric and surface quality for the deposits, a significant reduction in welding defects and an absence of spatter, is very sensitive to variations in the torch–piece distance and to changes of welding position. In this context, the present work deals with an analysis of the changes made to the position of the wire in relation to the electric arc and the weld bead, to the orientation of the torch in relation to the surface to be welded and to the welding parameters that make the plasma welding process more robust due to geometric alterations to the surface to be welded. The practical results achieved in the most critical situations, from the point of view of welding damaged surfaces, are presented with the objective of validating the changes proposed for the fed plasma process.     

Gel-derived SiO2–CaO–Na2O–P2O5 bioactive powders: Synthesis and in vitro bioactivity

In the present work, bioactive powders of the quaternary SiO₂–CaO–Na₂O–P₂O₅ system were synthesized by means of a sol–gel route. In their synthesis, tetraethoxysilane (Si(OC₂H₅)₄), calcium nitrate tetrahydrate (Ca(NO₃)₂? 4H₂O) and sodium nitrate (NaNO₃) were chosen as precursors of SiO₂, CaO and Na₂O, respectively. For P₂O₅, two different precursors were tested: triethylphosphate (OP(OC₂H₅)₃) and phosphoric acid (H₃PO₄). The gels were then converted into ceramic powders by heat treatments in the temperature range 700–1000 °C. The resulting materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) and in vitro bioactivity in acellular simulated body fluid (SBF). During the conversion of the gels into ceramics the mineralization behavior of the two sets of samples was different, but all the resulting materials were bioactive. The samples prepared using phosphoric acid exhibited the best in vitro bioactivity. This result was attributed to the preferential formation of bioactive sodium calcium silicate Na₂Ca₂Si₃O₉ crystals, especially in the samples submitted to heat treatments at 700 and 800 °C, which could not be observed in the samples prepared using triethylphosphate.     

基于灵活信号源的半导体器件检测（连载二）

图3显示了检测门限精度使用的波形设置。信号源是泰克AFG3000系列任意波形/函数发生器。该仪器的大型彩色屏幕显示所有相关参数设置及波形和幅值,从而简化了设置程序。脉冲的频率是10 kHz。     

The influence of positive polarity time on GTAW AC of aluminium

In this work, experiments were carried out to determine the welding behaviour of aluminium 1200 based on an increase in the activation time of the positive polarity for tungsten inert gas AC welding of this metal. To achieve this objective, a series of experiments was developed, in such a way that the intensity of the electrical current in the positive and negative polarities was the same; only the duration times in each polarity were modified. During the experiments, the current and voltage signals were acquired. In this way, the arc voltage and potential could be determined for each condition tested. In terms of the fusion behaviour, an increase in penetration and in welded areas was verified to the extent that longer positive polarity times were used. This behaviour is different from that commonly indicated in the literature about welding processes with non-consumable electrodes, which suggests a reduction in penetration with an increase in the positive polarity activation time. However, this trend grows constantly during the experiments from a determined point, where the positive polarity activity times are greater than 4.0 ms in a total period of 20.0 ms. The use of a minimum positive polarity time (1.3 ms) was shown to be effective for cathode cleaning, as it produced welds with satisfactory fusion characteristics and with minimum wear to the tungsten electrode. The good fusion capacity obtained in welds produced with long positive polarity times was attributed to phenomena arising from the emission of electrons due to the field effect that occurs during the positive electrode phases.     

Preparation and Characterization of the Novels Terpolymers of Poly-{trans-[RuCl2(vpy)4]-styrene-divinylbenzene} and Styrene-divinylbenzene-vinylpiridine impregnated with Silver Nanoparticles

This paper reports the preparation and characterization of poly-{trans-[RuCl₂(vpy)₄-styrene-divinylbenzene} and styrene-divinylbenzene-vinylpiridine filled with nanosilver. Theses materials were synthesized by non aqueous polymerization through a chemical reaction using benzoyl peroxide as the initiator. The nanosilver was obtained from chemical reduction using NaBH₄ as reducing agent and sodium citrate as stabilizer. The nanometric dimension of nanosilver was monitored by UV-visible and confirmed through TEM. The morphology was characterized by SEM and the thermal properties were done by TGA and DSC. The antimicrobial action of the polymers impregnated with nanosilver was evaluated using both microorganisms, Staphylococcus aureus and Escherichia coli. The antimicrobial activity of the poly-{trans-[RuCl₂(vpy)₄]-styrene-divinylbenzene} filled with nanosilver was confirmed by the presence of an inhibition halo of the bacterial growth in seeded culture media, but was not confirmed to the styrene-divinylbenzene-vinylpiridine. The present work suggest that trans - [RuCl₂(vpy)₄] complex facilitate the release of silver ion from the media.