Vitamin B-12 release from P(HEMA-co-THFMA) in water and SBF: A model drug release study

A model drug release study on the ingress of water and Kokubo simulated body fluid (SBF) into poly(2-hydroxyethyl methacrylate) (THFMA) and its copolymers with tetrahydrofurfuryl methacrylate (THFMA) loaded with vitamin B-12 was undertaken over the temperature range 298-318 K. The polymers were studied as cylinders and were loaded with either 5 or 10 wt-% of the drug. The drug release from the polymers was found to follow a Fickian diffusion mechanism in the early stages of the drug release, with higher normalized release rates at higher temperatures and higher drug loadings. The normalized release rates were also found to be higher for the SBF solution than for water. The copolymer composition was found to have a significant effect on the rate of release of the drug, with the rate falling rapidly between HEMA mole fractions of 1.0 and 0.8, but for lower mole fractions of HEMA the normalized release rate decreased more slowly. This behaviour followed the trend found for the changes in the equilibrium penetrant contents for the copolymers.

Matrix and reservoir-type multipurpose vaginal rings for controlled release of dapivirine and levonorgestrel

A matrix-type silicone elastomer vaginal ring providing 28-day continuous release of dapivirine (DPV) - a lead candidate human immunodeficiency virus type 1 (HIV-1) microbicide compound - has recently demonstrated moderate levels of protection in two Phase III clinical studies. Here, next-generation matrix and reservoir-type silicone elastomer vaginal rings are reported for the first time offering simultaneous and continuous in vitro release of DPV and the contraceptive progestin levonorgestrel (LNG) over a period of between 60 and 180days. For matrix-type vaginal rings comprising initial drug loadings of 100, 150 or 200mg DPV and 0, 16 or 32mg LNG, Day 1 daily DPV release values were between 4132 and 6113μg while Day 60 values ranged from 284 to 454μg. Daily LNG release ranged from 129 to 684μg on Day 1 and 2-91μg on Day 60. Core-type rings comprising one or two drug-loaded cores provided extended duration of in vitro release out to 180days, and maintained daily drug release rates within much narrower windows (either 75-131μg/day or 37-66μg/day for DPV, and either 96-150μg/day or 37-57μg/day for LNG, depending on core ring configuration and ignoring initial lag release effect for LNG) compared with matrix-type rings. The data support the continued development of these devices as multi-purpose prevention technologies (MPTs) for HIV prevention and long-acting contraception.

The potential of virulent Wolbachia to modulate disease transmission by insects

A virulent strain of Wolbachia has recently been identified in Drosophila that drastically reduces adult lifespan. It has been proposed that this phenotype might be introduced into insect disease vector populations to reduce pathogen transmission. Here we model the requirements for spread of such an agent and the associated reduction in disease transmission. First, a simulation of mosquito population age structure was used to describe the age distribution of mosquitoes transmitting dengue virus. Second, given varying levels of cytoplasmic incompatibility and fecundity effect, the maximum possible longevity reduction that would allow Wolbachia to invade was obtained. Finally, the two models were combined to estimate the reduction in disease transmission according to different introduction frequencies. With strong CI and limited effect of fecundity, an introduction of Wolbachia with an initial frequency of 0.4 could result in a 60–80% reduction of transmitting mosquitoes. Greater reductions are possible at higher initial release rates.

Augmentation of the assassin bug Pristhesancus plagipennis (Walker) (Hemiptera : Reduviidae) as a biological control agent for Helicoverpa spp. in cotton

Third-instar nymphs of the Australian assassin bug, Pristhesancus plagipennis (Walker), were released into cotton plots at two release densities and two crop growth stages to test their biological control potential. Release rates of 2 and 5 nymphs per metre row resulted in field populations of 0.51 and 1.38 nymphs per metre row, respectively, indicating that over 70% of nymphs died or emigrated within two weeks of release. Effective release rates of 1.38 nymphs per metre row reduced the number of Helicoverpa spp. larvae in the plots for a 7-week period. Crop yields were significantly greater in the plots to which P. plagipennis nymphs were released, with the effective release rate of 1.38 nymphs per metre row providing equivalent yields as insecticide treated plots. The data suggest that P. plagipennis has the capacity to reduce Helicoverpa spp. larvae densities in cotton crops when augmented through inundative release.

Factors affecting the establishment and dispersal of nymphs of Pristhesancus plagipennis Walker (Hemiptera : Reduviidae) when released onto soybean, cotton and sunflower crops

A problem with augmenting predatory bugs through mass release is the logistical difficulty of delivering nymphs onto the foliage of field crops. In this paper we examine postrelease establishment and dispersal of the nymphs of the predatory bug Pristhesancus plagipennis on soybean, cotton and sunflower in an effort to devise an appropriate strategy for field release. The effects of predator stadia and release rates on field establishment and within-crop-canopy dispersal after hand release were recorded in soybean, cotton and sunflower. Field establishment improved with the release of more-developed nymphs, with third instars providing the most appropriate compromise between field hardiness and rearing cost. Increased nymphal density at the point of release had little effect on nymphal dispersal throughout the crop canopy. The patterns of nymphal dispersal observed on the three crops suggest that crop-canopy architecture may have an effect on the ability of nymphs to spread out postrelease, as nymphs dispersed poorly in cotton and sunflower compared to soybean. To overcome poor dispersal of nymphs after release, a mechanical release method, where nymphs were mixed with vermiculite and delivered onto a target crop through a spinning disk fertiliser spreader, was tested, and provided similar nymph establishment rates and dispersal patterns as releasing nymphs individually by hand. The implications of nymph dispersal and field hardiness in regard to inundative field release techniques are discussed.

Influence of the cohesive law parameters on the strength prediction of adhesively-bonded joints

Adhesive joints are largely employed nowadays as a fast and effective joining process. The respective techniques for strength prediction have also improved over the years. Cohesive Zone Models (CZM’s) coupled to Finite Element Method (FEM) analyses surpass the limitations of stress and fracture criteria and allow modelling damage. CZM’s require the energy release rates in tension (Gn) and shear (Gs) and respective fracture energies in tension (Gnc) and shear (Gsc). Additionally, the cohesive strengths (tn0 for tension and ts0 for shear) must also be defined. In this work, the influence of the CZM parameters of a triangular CZM used to model a thin adhesive layer is studied, to estimate their effect on the predictions. Some conclusions were drawn for the accuracy of the simulation results by variations of each one of these parameters.

Determinação da tenacidade à fratura de adesivos estruturais em modo misto pelo ensaio Single-Leg Bending

A utilização de juntas adesivas em aplicações industriais tem vindo a aumentar, em detrimento dos métodos tradicionais tais como a soldadura, brasagem e ligações aparafusadas e rebitadas. Este facto deve-se às vantagens que estas oferecem, como o facto de serem mais leves, comportarem-se bem sob cargas cíclicas ou de fadiga, a ligação de materiais diferentes e menores concentrações de tensões. Para aumentar a confiança no projeto de estruturas adesivas, é importante conseguir prever com precisão a sua resistência mecânica e respetivas propriedades de fratura (taxa crítica de libertação de energia de deformação à tração, GIC, e corte, GIIC). Estas propriedades estão diretamente relacionadas com a Mecânica da Fratura e são estimadas através de uma análise energética. Para este efeito, distinguem-se três tipos de modelos: modelos que necessitam da medição do comprimento de fenda durante a propagação do dano, modelos que utilizam um comprimento de fenda equivalente e métodos baseados no integral J. Como na maioria dos casos as solicitações ocorrem em modo misto (combinação de tração com corte), é de grande importância a perceção da fratura nesta condições, nomeadamente das taxas de libertação de energia relativamente a diferentes critérios ou envelopes de fratura. Esta comparação permite, por exemplo, averiguar qual o melhor critério energético de rotura a utilizar em modelos numéricos baseados em Modelos de Dano Coesivo. Neste trabalho é realizado um estudo experimental utilizando o ensaio Single-Leg Bending (SLB) em provetes colados com três tipos de adesivos, de forma a estudar e comparar as suas propriedades de fratura. Para tal, são aplicados alguns modelos de redução da taxa de libertação de energia de deformação à tração, GI, e corte, GII, enquadrados nos modelos que necessitam da medição do comprimento de fenda e nos modelos que utilizam um comprimento de fenda equivalente. Numa fase posterior, procedeu-se à análise e comparação dos resultados adquiridos durante a fase experimental de GI e GII de cada adesivo. A discussão de resultados foi também feita através da análise dos valores obtidos em diversos envelopes de fratura, no sentido de averiguar qual o critério de rotura mais adequado a considerar para cada adesivo. Foi obtida uma concordância bastante boa entre métodos de determinação de GI e GII, com exceção do adesivo mais dúctil, para o qual o método baseado no comprimento de fenda equivalente apresentou resultados ligeiramente superiores.

Antibacterial properties of fibrous stents coated with silver oxide nanocoatings

Stents are rigid and perforated tubular structures, which are inserted into blood vessels in order to prevent or inhibit the constriction of blood flow, restoring the normal blood flow, when blood vessels are clogged, being used in 70% of angioplasties. These medical devices assume great importance in the treatment of cardiovascular diseases (CVD) which are the leading cause of death worldwide. In the European Union CVD account for 40% of deaths and assume an estimated annual cost of 196 billion euros[1]. Stents must possess certain requirements, in order to, adequately, perform its function, such as biocompatibility (so that its use does not c ause damage on the health of its user), mechanical strength, radiopacity (so that it is easy to view), longitudinal flexibility, ease of handling, corrosion resistance and having high strength and high radial expansion ability to recover. Stents can be made of different materials, but metals, particularly stainless steel, are the most common. However, metallic stents present several dRawbacks such as corrosion and restenosis, leading to health complications for the patient, or even death. In order to minimize these disadvantages, new materials, like fibrous materials, have been used [2]. Monofilaments present high potential for stents development because, in addition to its biocompatibility, these materials allow the application of various surface treatments, such as antibacterial coatings. Furthermore, monofilament exhibit excellent mechanical properties, like greater stiffness and good results when subjected to compression, tensile and bending forces, since these forces will be directly supported by the monofilament [3]. To minimize the reaction of the human body and Limit the adhesion of microorganisms to the stent surface, some coatings have been developed, including the use of novel metals with antimicrobial properties, like silver. The main objective of this study was the development of fibrous stents, incorporation of silver oxide nanocoating. For the development of the stent, polyester monofilaments with 0.27mm of diameter were used in braiding technology, with a mandrel diameter of 6mm and a braiding angle of 35⁰. The mechanical behaviour of the stent were evaluated by mechanical testing under longitudinal and radial compression, bending. The results of compressive strength tests are according with value from literature: 1.13 to 2.9 N for radial compression and 0. 16-5.28N to longitudinal compression. From literature is also possible to verify that stents must present 75% of unchanged diameter during the bending test and must possess a porosity between 70% and 80% [4]. The produced polyester stent presents values of 1.29N for radial compression, 0.23N for longitudinal compression, 80% of porosity and 85.5% of unchanged diameter, during bending tests. For the antibacterial functionalization, silver oxide nanocoatings were prepared, through reactive magnetron g, with an Ag target in an Ar +O2 atmosphere. In order to evaluate the nanostructure and morphology of the coatings, d ifferent technique s like X-ray diffraction (XRD), scanning electron microscopy (SEM) and and X- ray photoelectron spectroscopy (XPS were used. From the analyses of XRD it is possible to verify that the peaks corresponds to planes of Ag2 O and MATERIAIS 2015 Porto, 21-23 June, 2015 characterize a cubic phase. The presence of Ag2 O is corroborated by XPS spectrum, where it is possible to observe silver, not only, in oxide state, but a lso in mettalic state, and it is possible to verify the presence of silver clusters, confirmed by SEM analysis. Films’ roughness and topography, parameters influencing the wettability of the surface and microorganism adhesion, were measured by Atomic Force Microscopy (AFM), and it was observed that the roughness is very low (under 10 nm). Coatings’ hydrophobicity and surface tension parameters were determined by contact angle measurement, and it was verified the hydrophobic behavior of the coatings. For antibacterial tests were used Staphylococcus epidermidis strain (IE186) and Staphylococcus aureus(ATCC 6538), and halo inhibition zone tests were realized. Ag+release rates were studied by means of inductively coupled plasma mass spectrometry (ICP -MS). The obtained results suggest that silver oxide coatings do not modify significantly surface properties of the substrate, like hydrophobicity and roughness, and present antimicrobial properties for both bacteria used.

Carbon and nitrogen cycling in an integrated soybean-beef cattle production system under different grazing intensities

Abstract:The objective of this work was to evaluate the effect of grazing intensity on the decomposition of cover crop pasture, dung, and soybean residues, as well as the C and N release rates from these residues in a long-term integrated soybean-beef cattle system under no-tillage. The experiment was initiated in 2001, with soybean cultivated in summer and black oat + Italian ryegrass in winter. The treatments consisted of four sward heights (10, 20, 30, and 40 cm), plus an ungrazed area, as the control. In 2009-2011, residues from pasture, dung, and soybean stems and leaves were placed in nylon-mesh litter bags and allowed to decompose for up to 258 days. With increasing grazing intensity, residual dry matter of the pasture decreased and that of dung increased. Pasture and dung lignin concentrations and C release rates were lower with moderate grazing intensity. C and N release rates from soybean residues are not affected by grazing intensity. The moderate grazing intensity produces higher quality residues, both for pasture and dung. Total C and N release is influenced by the greater residual dry matter produced when pastures were either lightly grazed or ungrazed.

β-Adrenergic modulation of skeletal muscle contraction: key role of excitation-contraction coupling.

Our aim is to describe the acute effects of catecholamines/β-adrenergic agonists on contraction of non-fatigued skeletal muscle in animals and humans, and explain the mechanisms involved. Adrenaline/β-agonists (0.1-30 μm) generally augment peak force across animal species (positive inotropic effect) and abbreviate relaxation of slow-twitch muscles (positive lusitropic effect). A peak force reduction also occurs in slow-twitch muscles in some conditions. β2 -Adrenoceptor stimulation activates distinct cyclic AMP-dependent protein kinases to phosphorylate multiple target proteins. β-Agonists modulate sarcolemmal processes (increased resting membrane potential and action potential amplitude) via enhanced Na(+) -K(+) pump and Na(+) -K(+) -2Cl(-) cotransporter function, but this does not increase force. Myofibrillar Ca(2+) sensitivity and maximum Ca(2+) -activated force are unchanged. All force potentiation involves amplified myoplasmic Ca(2+) transients consequent to increased Ca(2+) release from sarcoplasmic reticulum (SR). This unequivocally requires phosphorylation of SR Ca(2+) release channels/ryanodine receptors (RyR1) which sensitize the Ca(2+) -induced Ca(2+) release mechanism. Enhanced trans-sarcolemmal Ca(2+) influx through phosphorylated voltage-activated Ca(2+) channels contributes to force potentiation in diaphragm and amphibian muscle, but not mammalian limb muscle. Phosphorylation of phospholamban increases SR Ca(2+) pump activity in slow-twitch fibres but does not augment force; this process accelerates relaxation and may depress force. Greater Ca(2+) loading of SR may assist force potentiation in fast-twitch muscle. Some human studies show no significant force potentiation which appears to be related to the β-agonist concentration used. Indeed high-dose β-agonists (∼0.1 μm) enhance SR Ca(2+) -release rates, maximum voluntary contraction strength and peak Wingate power in trained humans. The combined findings can explain how adrenaline/β-agonists influence muscle performance during exercise/stress in humans.

Dustiness and deagglomeration testing: interlaboratory comparison of systems for nanoparticle powders

Different types of aerosolization and deagglomeration testing systems exist for studying the properties of nanomaterial powders and their aerosols. However, results are dependent on the specific methods used. In order to have well-characterized aerosols, we require a better understanding of how system parameters and testing conditions influence the properties of the aerosols generated. In the present study, four experimental setups delivering different aerosolization energies were used to test the resultant aerosols of two distinct nanomaterials (hydrophobic and hydrophilic TiO2). The reproducibility of results within each system was good. However, the number concentrations and size distributions of the aerosols created varied across the four systems; for number concentrations, e.g., from 10(3) to 10(6) #/cm(3). Moreover, distinct differences were also observed between the two materials with different surface coatings. The article discusses how system characteristics and other pertinent conditions modify the test results. We propose using air velocity as a suitable proxy for estimating energy input levels in aerosolization systems. The information derived from this work will be especially useful for establishing standard operating procedures for testing nanopowders, as well as for estimating their release rates under different energy input conditions, which is relevant for occupational exposure.

Corrosion resistance improvement of titanium base alloys

The corrosion resistance of the new Ti-6Al-4V-1Zr alloy in comparison with ternary Ti-6Al-4V alloy in Ringer-Brown solution and artificial Carter-Brugirard saliva of different pH values was studied. In Ringer-Brown solution, the new alloy presented an improvement of all electrochemical parameters due to the alloying with Zr; also, impedance spectra revealed better protective properties of its passive layer. In Carter-Brugirard artificial saliva, an increase of the passive film thickness was proved. Fluoride ions had a slight negative influence on the corrosion and ion release rates, without to affect the very good stability of the new Ti-6Al-4V-1Zr alloy.

Study of the diffusion in polymer solutions and hydrogels by NMR spectroscopy and NMR imaging

Afin d'étudier la diffusion et la libération de molécules de tailles inférieures dans un gel polymère, les coefficients d'auto-diffusion d'une série de polymères en étoile avec un noyau d'acide cholique et quatre branches de poly(éthylène glycol) (PEG) ont été déterminés par spectroscopie RMN à gradient de champ pulsé dans des solutions aqueuses et des gels de poly(alcool vinylique). Les coefficients de diffusion obtenus ont été comparés avec ceux des PEGs linéaires et dendritiques pour étudier l'effet de l'architecture des polymères. Les polymères en étoile amphiphiles ont des profils de diffusion en fonction de la concentration similaires à leurs homologues linéaires dans le régime dilué. Ils diffusent plus lentement dans le régime semi-dilué en raison de leur noyau hydrophobe. Leurs conformations en solution ont été étudiées par des mesures de temps de relaxation spin-réseau T1 du noyau et des branches. L'imagerie RMN a été utilisée pour étudier le gonflement des comprimés polymères et la diffusion dans la matrice polymère. Les comprimés étaient constitués d'amidon à haute teneur en amylose et chargés avec de l'acétaminophène (de 10 à 40% en poids). Le gonflement des comprimés, ainsi que l'absorption et la diffusion de l'eau, augmentent avec la teneur en médicament, tandis que le pourcentage de libération du médicament est similaire pour tous les comprimés. Le gonflement in vitro des comprimés d'un complexe polyélectrolyte à base d'amidon carboxyméthylé et de chitosane a également été étudié par imagerie RMN. Ces comprimés sont sensibles au pH : ils gonflent beaucoup plus dans les milieux acides que dans les milieux neutres en raison de la dissociation des deux composants et de la protonation des chaînes du chitosane. La comparaison des résultats avec ceux d'amidon à haute teneur en amylose indique que les deux matrices ont des gonflements et des profils de libération du médicament semblables dans les milieux neutres, alors que les comprimés complexes gonflent plus dans les milieux acides en raison de la dissociation du chitosane et de l'amidon.

Formulation development and characterization of liquisolid tablets containing clozapine

L’objectif de ce projet était de développer une formulation liquisolide (LS) de clozapine ayant des propriétés de dissolution améliorées et évaluer sa stabilité et ainsi que sa robustesse à la modification d’excipients. Le propylène glycol (PG), la cellulose microcrystalline (MCC) et le glycolate d’amidon sodique (SSG) ont été utilisés respectivement en tant que véhicule liquide non volatile, agent de masse et agent désintégrant pour la préparation de comprimés LS. Le dioxyde de silicium colloïdal (CSD), le silicate de calcium (CS) et l'aluminométasilicate de magnésium (MAMS) ont été choisis comme agents d’enrobage sec. La caractérisation complète des mélanges et des comprimés a été effectuée. Le taux de libération des comprimés LS était statistiquement supérieur à celui des comprimés réguliers. La surface spécifique des matériaux d’enrobage avait un effet sur les propriétés d’écoulement des mélanges et la taille des particules des matériaux d’enrobage a eu un effet sur la vitesse de dissolution. Le ratio support/enrobage du mélange de poudres (valeur de R) était un paramètre important pour les systèmes LS et devait être plus grand que 20 afin d’obtenir une meilleure libération du médicament. La formulation choisie a démontré une stabilité pour une période d’au moins 12 mois. La technique LS s’est avéré une approche efficace pour le développement de comprimés de clozapine ayant des propriétés de dissolution améliorées. Les comprimés oro-dispersibles (ODT) sont une formulation innovante qui permettent de surmonter les problèmes de déglutition et de fournir un début d'action plus rapide. Dans l’optique d’améliorer les propriétés de dissolution, un essai a été effectué pour étudier la technique LS dans la formulation des ODT de clozapine. Le PG, la MCC, le CSD et la crospovidone (CP) ont été utilisés respectivement en tant que véhicule liquide non volatile, agent de masse, agent d’enrobage sec et agent superdésintégrant pour la préparation de comprimés oro-dispersibles liquisolides (OD-LST). Le mannitol a été choisi comme agent de masse et agent édulcorant. La saccharine de sodium a été utilisée comme agent édulcorant. La caractérisation complète des comprimés a été effectuée. Le taux de libération des OD-LSTs était statisquement supérieur comparativement aux comprimés ODTs. La formulation choisie a démontré une stabilité pour une période d’au moins 6 mois. Il a été conclu que des ODT de clozapine peuvent être préparés avec succès en utilisant la technologie LS dans le but d’améliorer la désintégration et le taux de dissolution de la clozapine dans la cavité orale.

Analysis of total visual and CCD V-broadband observations of Comet C/1995 O1 (Hale-Bopp): 1995-2001

We developed a general method for determination of water production rates from groundbased visual observations and applied it to Comet Hale-Bopp. Our main objective is to extend the method to include total visual magnitude observations obtained with CCD detector and V filter in the analysis of total visual magnitudes. We compare the CCD V-broadband careful observations of Liller [Liller, W. Pre-perihelion CCD photometry of Comet 1995 01 (Hale-Bopp). Planet. Space Sci. 45, 1505-1513, 1997; Liller, W. CCD photometry of Comet C/1995 O1 (Hale-Bopp): 1995-2000. Int. Comet Quart. 23(3), 93-97, 2001] with the total visual magnitude observations from experienced international observers found in the International Comet Quarterly (ICQ) archive. A data set of similar to 400 CCD observations covering about the same 6 years time span of the similar to 12,000 ICQ selected total visual magnitude observations were used in the analysis. A least-square method applied to the water production rates, yields power laws as a function of the heliocentric distances for the pre- and post-perihelion phases. The average dimension of the nucleus as well as its effective active area is determined and compared with values published in the literature. (C) 2009 COSPAR. Published by Elsevier Ltd. All rights reserved.