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PubMed1956

A malaria-control experiment in the interior of Borneo.

A first experiment on malaria control in the interior of Borneo by spraying with residual insecticides is described. The work was carried out in the isolated, sparsely populated valleys of the Baram River and its tributary, the Tinjar, in northern Sarawak. The experimental area was divided into three parts: a DDT test area, where a 75% suspension of wettable powder was applied at the rate of 2 g of DDT per m(2) of surface; a BHC test area, where a 50% suspension of wettable powder was applied at the rate of 0.10 g of gamma isomer per m(2); and a check area.Entomological investigations made before the spraying operations were started showed that Anopheles leucosphyrus Dönitz, 1901 was the main malaria vector in both the test and the check areas. Out of a total of 7568 A. leucosphyrus dissected, 30 gland infections were detected-a sporozoite-rate of 0.40%. A. barbirostris was found to be a secondary vector throughout the experimental area.THE RESULTS OF INSECTICIDE SPRAYING WERE SATISFACTORY: in the DDT test area, the spleen-rate fell from 51.8% to 25.1%, and the parasite-rate from 35.6% to 1.6%, in 21 months, and a similar reduction in the rates was observed in the BHC test area. In the check area, the spleen- and parasite-rates rose during the period of observations. It is considered that if such a degree of control can be obtained in 21 months, complete eradication can be expected in the near future.Although BHC spraying proved effective, the fact that it has to be repeated every three months makes it impracticable in the interior of Sarawak, where communications are very poor and difficulties of transport very great. DDT spraying, which need only be done twice a year, is therefore to be preferred. The cost of the DDT operations-US$ 0.45 per person protected per year-is comparatively high, owing to the difficulty of communications and to the necessity for spraying not only the village "longhouses", but also the temporary shelters which the semi-nomadic people in the interior of Sarawak build each year in the rice-fields.

Animals↗

PubMed1990

[Study on postsoldering of Ni-Cr ceramic alloys. Effect of soldering temperature and atmosphere].

The effects of soldering temperatures and atmospheres on tensile strength of solder joints were investigated for two types of Ni-Cr ceramic alloys and one type of gold solder for postsoldering. Each alloy and the gold solder were soldered with fluoride flux in an electric furnace in three different temperatures and four different atmospheres. Of the three different temperatures, one was just over the liquidus point of the solder, another 50 degrees C higher than the liquidus point and the other 100 degrees C higher than the liquidus point. Of the four different atmospheres, one was under vacuum, another under vacuum with a 6 l/h argon gas flow, another under vacuum with a 12 l/h argon gas flow and the other under vacuum with a 24 l/h argon gas flow. Tensile strength testing was performed at the solder joints. The fracture surface was observed by EPMA. Wettability of the liquid solder on each alloy was performed by the sessile drop method in high-purity argon gas. The surface tension and the contact angle of the liquid solder on MgO were determined by the sessile drop method in high-purity argon gas. The soldering was performed in the furnace used for the sessile drop method in high-purity argon gas. The results are summarized as follows. The tensile strength of UNI METAL-solder joints was significantly affected by the soldering temperature (p less than 0.01). However, the effect of the soldering atmosphere on the tensile strength was small. The effect of the soldering temperature and atmosphere on the tensile strength of Victory II-solder joints was small. Each alloy had a different adequate soldering temperature. With the increase in the soldering temperature, the diffusion layer of the solder joint interface increased, but no correlationship between the atmosphere and the diffusion layer thickness was observed. Fracture patterns of UNI METAL-solder joints were mixed adhesive-cohesive fractures with a large cohesive area. Fracture patterns of Victory II-solder joints were mixed adhesive-cohesive fractures with a large adhesive area. It was possible to perform the soldering without flux in the furnace used for the sessile drop method in a strictly controlled atmosphere of high-purity argon gas. Wettability of the liquid solder on UNI METAL was better than on Victory II. The surface tension of the solder used was 505.9 dyn/cm at 1000 degrees C. The contact angle of the solder used was 163.0 degrees at 1000 degrees C.

Chromium Alloys↗

PubMed1989

[Effect of sandblast treatment on resin-alloys bond strength by silicoating technique].

The purpose of this study was to investigate why sandblast treatment increases the bond strength of resin-alloy by the Silicoating technique. In this study, two types of alloy specimens, namely Ag-Pd alloy and Ni-Cr alloy, were prepared by casting. These specimens were given sandblast treatment by 37 microns or 250 microns Al2O3 particle under the following conditions: 3 kg/cm2 for 30 sec, 5 kg/cm2 for 10 sec, 30 sec and 45 sec, and 7 kg/cm2 for 30 sec. Under each condition of sandblast treatment, changes in roughness and wettability of the alloy surface were measured. After this treatment, the alloy surface was Silicoated, and then a light-cured resin was bonded to it. Specimens were stored in air for one week and thermal cycled from 4 to 60 degrees C for 10(4) cycles. The bond strength was measured by compressive shear stress. It was shown that the sandblast treatment caused the surface area to increase in the range of 1.3-1.9 times. Also, the sandblast treatment made the alloy-water contact angle smaller and wettability greater. Maximum bond strengths for Ag-Pd alloy and Ni-Cr alloy, when sandblast treated and stored in the air for one week, were 213.7 kg/cm2 and 198.7 kg/cm2 respectively. On the other hand, bond strengths for Ag-Pd alloy and Ni-Cr alloy after thermal cycling were 129.5 kg/cm2 and 159.9 kg/cm2 respectively. These values of bond strength were 2-3 times greater than those of for specimens not given the sandblast treatment. However, varying the conditions of sandblast treatment did not produce any significant differences.

Chromium Alloys↗

PubMed1987

Laboratory and field efficacy of Bacillus thuringiensis var. Israelensis and Bacillus sphaericus against Anopheles gambiae s.l. and Culex quinquefasciatus in Ouagadougou, Burkina Faso.

Two wettable powders (Bactimos and Vectobac) and one flowable concentrate (Teknar) of Bacillus thuringiensis var. israelensis (B.t.i.) and primary powders of Bacillus sphaericus isolates 1593 and 2362 were evaluated (laboratory) against field-collected larvae of Anopheles gambiae s.l. and Culex quinquefasciatus in Ouagadougou, Burkina Faso. Bactimos, Vectobac and a Corn-cob B.t.i. formulation (ABG-6138G) were field tested against Cx. quinquefasciatus and An. gambiae s.l. The isolates of B. sphaericus were also tested against An. gambiae s.l. in artificial ponds. Both wettable powders of B.t.i. showed superior activity than the flowable concentrate formulation against An. gambiae s.l. in the laboratory. Culex quinquefasciatus was more susceptible (3-4X) to B.t.i. (Bactimos) than An. gambiae s.l. The isolates of B. sphaericus were more effective (2-3X) against both mosquito species than Bactimos. In a ditch and two channels, Bactimos, Vectobac and ABG-6138G at 0.65, 1.5 and 5.6 kg/ha, respectively, gave 91-100% control of Cx. quinquefasciatus within 3 days of treatment. The same formulations at rates ranging from 0.25 to 5.6 kg/ha, produced 82-97% control of An. gambiae s.l. in rainwater pools 24 h after treatment. Isolates 1593 and 2362 at 0.12 and 0.24 kg/ha gave excellent control of An. gambiae s.l. in artificial ponds.

Animals↗

PubMed1966

Testing blackfly larvicides in the laboratory and in streams.

The early discovery that DDT is extremely effective in controlling blackfly larvae led to its widespread use in control programmes. Recent evidence that DDT accumulates in the food chain has made it desirable to investigate the effectiveness of other, less persistent, insecticides in reducing populations of blackfly larvae.A method of testing larvicides in troughs was developed and tests were carried out with a number of insecticides both in the troughs and in streams in New York State. Fourfold or fivefold differences in the susceptibility of larvae to different formulations of the same chemical were noted. In the laboratory, emulsions were less effective than oil solutions or wettable-powder suspensions. The effectiveness of emulsions under field conditions, noted in the course of their widespread use in Africa, may be due to the ease with which they become uniformly distributed throughout the water even when no special effort is made to ensure even distribution. When aircraft are used to apply larvicides in oil solution the insecticide is similarly distributed in fine droplets resulting in control at unusually low dosages.In trough tests and in streams, methoxychlor and DDT in oil solutions were about equally effective; carbaryl in wettable-powder suspension was highly effective in the laboratory but relatively greater concentrations were required in streams. Abate in oil solution was effective at low dosages in the laboratory and, in a single test, in a stream.

Animals↗

PubMed1969

A standard and rapid method for determining nozzle-tip abrasion.

The wear resistance of nozzle tips used in malaria eradication programmes has, in the past, been measured with water suspensions of a variety of wettable powder insecticides. The abrasive powers of these suspensions vary greatly, and it is therefore impossible to relate the results of one test to those of another. A standard method has been devised in which a suspension of a standard synthetic powder with a high silica content is forced through nozzles, once, at 40 lbf/in(2) (2.81 kgf/cm(2)). The method is reliable, reproducible, and rapid, and it may also be used to evaluate the abrasiveness of water-wettable insecticide powders.

Equipment and Supplies↗

PubMed1984

[Experimental studies of Dallon vascular prostheses after superficial alkaline hydrolysis].

Within the research on improving polyester vascular prostheses DALLON there was made a superficial alkaline hydrolysis in the manufactured product, which greatly enhanced the prostheses wettability without lowering their resistance parameters. In preliminary laboratory research and in biological studies in vitro, made with model prostheses and with those having been hydrolyzed, the results were better for hydrolized ones. Biological studies in vivo were made on piglets by implanting the prostheses into surgical defects of the thoracic aorta. In the course of the operations it was found that the prostheses were, apart from having better wettability, far more tight intraoperationally, as compared to the model ones. Pathomorphological studies, carried out 3 and 6 months after the operation, showed that, besides the hydrolized prostheses being less calcified, there were no significant qualitative and quantitative changes in the tissues around the implanted prostheses.

Animals↗

PubMed1993

Characteristics of metal and ceramic total hip bearing surfaces and their effect on long-term ultra high molecular weight polyethylene wear.

The micromechanics of ultra high molecular weight polyethylene (UHMWPE) wear in total hip replacement are very complex. Polyethylene wear from the metal head and debris formation are two common types of wear. There are additional wear-related processes occurring at the metal-bearing surfaces that are not well-known, however. This study outlines these processes, including (1) surface wettability changes, (2) oxidative wear of metal surfaces, (3) microabrasion of metal surfaces from oxide film damage, and (4) surface abrasion from three-body polymethylmethacrylate and bone debris. These processes can contribute to metal ion release and a gradual increase in the roughness of the metal surfaces. This can lead to increased long-term UHMWPE wear. Of the metal alloys currently used in total hip replacements, Co-Cr-Mo alloy is significantly more resistant to roughening processes. Hard, stable, oxide: ceramic surfaces articulating against UHMWPE are essentially immune to these surface-roughening processes, however. In addition, they provide a more wettable surface, further minimizing polyethylene wear relative to metal surfaces. By analyzing metal release rates from metal-polyethylene wear tests, it is shown here that Co-Cr-Mo is gradually removed at a rate of about 0.1 micron per year (10(6) cycles), whereas 316L stainless steel is removed on the order of 0.2 microns per year and Ti-6Al-4V on the order of 1 micron per year. The wear rate of Co-Cr-Mo articulating against itself is reported to be still greater, at about 2-4 microns per year after an initial wear-in period. Because metal is gradually removed with articulation time, surface-hardening methods such as nitrogen ion implantation can be expected to provide only temporary resistance to these metal removal and surface-roughening processes. Hard, stable ceramic surfaces such as Al2O3 and ZrO2, however, can be expected to maintain their initial surface finish and thus minimize UHMWPE wear in the long term.

Alloys↗

PubMed1998

Ovicidal activity of neem products (azadirachtin) against Culex tarsalis and Culex quinquefasciatus (Diptera: Culicidae).

Bioactive compounds contained in the seed kernel and other parts of the neem tree (Azadirachta indica A. Juss) have been found to show insecticidal activities and other effects in many species of insects. These activities include antifeedancy, growth regulation, fecundity suppression, male sterility, oviposition repellency, changes in biological fitness such as loss of flying ability, immunodepression, enzyme inhibition, splitting of biological rhythms, and so forth. We investigated the ovicidal effects of various formulations of azadrirachtin (AZ) against the mosquitoes Culex tarsalis Coquillett and Culex quinquefasciatus Say. The formulations tested were wettable powder Azad WP10, emulsifiable concentrate Azad EC4.5, and technically pure AZ. The ovicidal activity of the test neem products was influenced by concentration of AZ, age of the egg rafts, and age of the neem preparations. Other factors such as formulation and mosquito species were also involved in the degree of ovicidal activity. When the egg rafts were deposited directly in fresh neem suspension and left there for 4 h before transfer to untreated water, 1 ppm of AZ produced almost 100% mortality in eggs. When egg rafts aged for 0, 4, 8, 12, and 24 h were exposed to 10 ppm neem suspensions for 36 h, the ovicidal activity was only attained in the egg rafts deposited directly (0 h old) in the neem suspension, not in those with ages of 4-24 h. On aging, depending on the formulations and mosquito species, the neem suspensions at 1 ppm completely lost ovicidal activity within 7-20 days. The egg rafts of Cx. quinquefasciatus were more susceptible to the test neem products than those of Cx. tarsalis. The formulated neem products were more persistent and effective than the technical AZ. The wettable powder (WP) formulation was slightly more persistent and effective than the emulsifiable concentrate (EC). The ovicidal activity of the neem products against mosquitoes from the current research clearly demonstrated the potential of neem products as possible ovicides against Culex mosquitoes.

Animals↗

PubMed2004

Neurotransmitter analog tethered to a silicon platform for neuro-BioMEMS applications.

The design of chemically well-defined, machinable surfaces containing neuroactive molecules offers potential for fundamental neuroscience and clinical neural engineering applications. Here we report the assembly and characterization of silicon platforms containing a tethered form of muscimol. Muscimol, an analog of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), is a potent agonist at postsynaptic GABA(A) and GABA(C) receptors. Surfaces were assembled using covalent avidin conjugation to silanized silicon followed by high-affinity avidin-biotin binding of a biotinylated derivative of muscimol (muscimol-biotin). Contact angle measurements, ellipsometry, and X-ray photoelectron spectroscopy (XPS) were conducted to characterize the wettability, thickness, and chemical composition of progressively deposited surface layers. The data demonstrate successful incorporation of a neurotransmitter analog as part of a layered, silicon-based structure possessing robust and specific biomolecular composition. These findings represent a step toward the design of platforms for applications involving control and modulation of neural signaling.

Avidin↗

PubMed2002

Adsorption/desorption phenomena on pure and Teflon AF-coated titania surfaces studied by dynamic contact angle analysis.

As a result of inflammatory processes, plaque formation on dental titanium implants often leads to clinically pathogenic situations. This special biofilm formation on (bio)materials in contact with saliva is initiated by ionic and protein interactions. In this interfacial process, albumin becomes a main constituent of dental pellicle. Interfacial reactions change the surface characteristics. They determine the following steps of macromolecular adsorption and bacterial adhesion. This work focuses on the dynamic contact angle analysis (DCA), which is a tool for online measurements of dynamic changes of wettability without disturbing the interface during detection. Repeatability of the DCA method has been assessed according to the Bland and Altman method. The kinetics and equilibrium data of shifts in the wetting tension hysteresis indicate ionic influences at the titanium/bovine serum albumin (BSA) interface: the Ca-mediated increase of the BSA adsorption on titanium and the adsorption maximum at the isoelectric point (IEP) of BSA. Ti was surface modified by Teflon AF polymeric coatings. The result of the assessment gives reason to consider Teflon AF as a reference material for DCA repeatability studies. This surface modification caused drastic changes in the dynamic interfacial reactions. Shifts in the wetting tensions during DCA adsorption-desorption experiments clearly demonstrated the partially irreversible adsorption of BSA on Teflon AF. In contrast, reversible adsorption behavior was detected on pure Ti surfaces. These findings strengthen the hypothesis that the analysis of dynamic changes in wetting tension and wetting tension hysteresis is a sensitive analytical method for the detection of dynamic interfacial changes at biomaterial/biosystem interfaces during the initial steps of biofilm formation.

Adsorption↗

PubMed2004

Endothelial cell functions in vitro cultured on poly(L-lactic acid) membranes modified with different methods.

We recently developed several methods to enhance the cell-polymer interactions. Optimal conditions for each method have been revealed separately by in vitro cell culture. As a practical consideration for construction of tissue-engineered organs, it is necessary to consider which is the most suitable and convenient in clinical applications. To compare the efficiency of these methods with respect to cell functions, poly-L-lactic acid (PLLA) was selected as matrix being modified by 1) aminolysis (PLLA-NH(2)), 2) collagen immobilization with GA (PLLA-GA-Col), 3) chondroitin sulfate (CS)/collagen layer-by-layer (LBL) assembly (PLLA-CS/Col), 4) photo-induced grafting copolymerization of hydrophilic methacrylic acid (MAA) (PLLA-g-PMAA), and 5) further immobilization of collagen with 1-ethyl-3-(3-dimethylamino propyl) carbodiimide hydrochloride (EDAC) (PLLA-g-PMAA-Col). The surface wettability of the modified PLLA was determined by water contact angle measurements. The cell response to the modified PLLA was quantitatively assessed and compared by using human umbilical endothelial cells (HUVECs) culture. Our results indicate that all the modifications can improve the cytocompatibility of PLLA (e.g., cells can attach with spreading morphology, proliferate and secret vWF and 6-keto-PGF(1 alpha)). All the collagen-modified PLLA showed more positive cell response than those purely aminolyzed or PMAA grafted. Among all the methods, collagen immobilization by LBL assembly or GA bridging after aminolysis is more acceptable for the convenience and applicability to scaffolds.

Biocompatible Materials↗

PubMed2005

Scaled interfacial activity of proteins at a hydrophobic solid/aqueous-buffer interface.

Contact-angle goniometry confirms that interfacial energetics of protein adsorption to the hydrophobic solid/aqueous-buffer (solid-liquid, SL) surface is not fundamentally different than adsorption to the aqueous-buffer/air (liquid-vapor, LV) interface measured by pendant-drop tensiometry. Adsorption isotherms of 9 globular blood proteins with molecular weight (MW) spanning from 10 to 1000 kDa on methyl-terminated self-assembled monolayer surfaces demonstrate that (i) proteins are weak surfactants, reducing contact angles by no more than about 15 degrees at maximum solution concentrations ( approximately 10 mg/mL); (ii) the corresponding dynamic range of spreading pressure Pi(a) < 20 mN/m; and (iii) the maximum spreading pressure Pi(max) (a) for these diverse proteins falls within a relatively narrow 5 mN/m band. As with adsorption to the LV interface, we find that concentration scaling substantially alters perception of protein interfacial activity measured by Pi(a). Proteins appear more similar than dissimilar on a weight/volume basis whereas molarity scaling reveals a systematic ordering by MW, suggesting that adsorption is substantially driven by solution concentration rather than diversity in protein amphilicity. Scaling as a ratio-to-physiological-concentration demonstrates that certain proteins exhibit Pi(max)(a) at-and-well-below physiological concentration whereas others require substantially higher solution concentration to attain Pi(max)(a). Important among this latter category of proteins is blood factor XII, assumed by the classical biochemical mechanism of plasma coagulation to be highly surface active, even in the presence of overwhelming concentrations of other blood constituents such as albumin and immunoglobulin that are shown by this work to be among the class of highly surface-active proteins at physiologic concentration. The overarching interpretation of this work is that water plays a dominant, controlling role in the adsorption of globular-blood proteins to hydrophobic surfaces and that energetics of hydration control the amount of protein adsorbed to poorly water-wettable biomaterials.

Adsorption↗

PubMed2007

Acrylic bone cements with bismuth salicylate: Behavior in simulated physiological conditions.

In a previous work, we reported the development of acrylic bone cement formulations for application in percutaneous vertebroplasty, by using bismuth salicylate (BS) as the radiopaque agent. Our objective was to obtain high radiopacity along with a therapeutical effect produced by the release of salicylic acid in situ. To follow that study, the setting kinetics and static and dynamical mechanical properties of the BS cements were studied in simulated physiological conditions. Moreover, radiopacity after various times of immersion in saline and the wettability of the cements surfaces were determined. The study finished with the analysis of the biological response. From the results, it can be concluded that physiological conditions did not affect negatively to the cements performance, since all BS-loaded cements fulfilled the ISO standard requirements. Radiopacity of the formulations was maintained over time and cements with BS were found to be biocompatible.

Acrylates↗

PubMed2006

Microscopic observation of unworn siloxane-hydrogel soft contact lenses by atomic force microscopy.

In the present study, samples of lotrafilcon A, balafilcon A, and galyfilcon A contact lenses were observed by atomic force microscopy (AFM) in tapping mode at areas ranging from 0.25 to 400 microm2. Mean roughness (Ra), root-mean-square roughness (Rms) and maximum roughness (Rmax) in nanometers were obtained for the three lens materials at different magnifications. The three contact lenses showed significantly different surface topography. However, roughness values were dependent of the surface area to be analyzed. For a 1 microm2 area, statistics revealed a significantly more irregular surface of balafilcon A (Ra = 6.44 nm; Rms = 8.30 nm; Rmax = 96.82 nm) compared with lotrafilcon A (Ra = 2.40 nm; Rms = 3.19 nm; Rmax = 40.89 nm) and galyfilcon A (Ra = 1.40 nm; Rms = 1.79 nm; Rmax = 15.33 nm). Ra and Rms were the most consistent parameters, with Rmax presenting more variability for larger surface areas. The higher roughness of balafilcon A is attributed to the plasma oxidation treatment used to improve wettability. Conversely, galyfilcon A displays a smoother surface. Present observations could have implications in clinical aspects of siloxane-hydrogel contact lens wear such as lens spoliation, resistance to bacterial adhesion, or mechanical interaction with the ocular surface.

Contact Lenses, Hydrophilic↗

PubMed2006

An improved hydrophilicity via electrospinning for enhanced cell attachment and proliferation.

The wettability of electrospun poly(epsilon-caprolactone) (PCL) mats was improved by co-electrospinning with poly(vinyl alcohol) (PVA), by double-spinneret electrospinning method. The improved hydrophilicity of the hybrid PCL/PVA mats was confirmed by water contact angle measurement. The in vitro cell attachment on the hydrophobic PCL and hydrophilically modified PCL/PVA mats was compared by culture studies using human prostate epithelial cells (HPECs). The stability of water-soluble PVA component in the electrospun PCL/PVA mats was checked by thermogravimetric analysis and intensity of fluorescence material after immersion in water for 7 days. The images from scanning electron microscopy, field emission scanning electron microscopy, and optical microscopy showed that the attachment and proliferation rate of HPECs were improved by introducing PVA into the electrospun PCL mats.

Cell Adhesion↗

PubMed2002

Face specific surface properties of pharmaceutical crystals.

A variety of surface specific techniques have been used to determine the face-specific structure, chemistry, and wettability of model pharmaceutical crystals, i.e., N,n-octyl-d-gluconamide and sulfathiazole (polymorphic forms I and III). The surface energetics of individual crystal faces were investigated by studying their wetting characteristics and interaction with chemically modified silica spheres using colloid probe atomic force microscopy (AFM). Contact angles (dynamic and static), interaction forces, and adhesion properties have been shown to correlate strongly with the face specific surface chemistry. This, in turn, is controlled by the molecular arrangement at the specific crystal face, which has been characterized by time-of-flight secondary-ion mass spectrometry (ToF SIMS) and inferred from molecular models. Of specific note, the magnitude of the adhesion force between a crystal face and a hydrophobic colloid probe is related linearly to the face-specific equilibrium contact angle. These studies further our understanding of the face-specific properties of pharmaceutical crystals and have implications when considering processing, formulation and delivery.

Chemical Phenomena↗

PubMed2000

Femoral prosthetic heads and their significance in polyethylene wear.

We used scanning electron microscopy to perform an ultrastructural analysis and two optical interferometric profilers to measure roughness on 40 prosthetic femoral heads. We expressed roughness as Ra (roughness average) value and Rsk (roughness skewness) value. Our results show that in order to obtain an ideal surface finish a low or not very high Ra value and a negative Rsk value are needed. The presence of depressions or holes (rather than scratches) with smooth (rather than sharp) edges seems to improve the lubrication and wettability properties.

Ceramics↗