Fabrication of PVA-Silver nanoparticle composite film for elimination of microbial contaminant from effluent

The effluent contains many harmful microbes which should be eliminated before it is discharged into a water body. Silver nanoparticles (AgNPs) being high-quality significance and have a great impact on this research field as it inhibits microbial proliferation and infection. Therefore, it may use for Bioremediation purposes, our laboratory is fascinated by the production of polymer matrix entrapment silver nanoparticles for in situ bio-remediation purposes. The AgNPs was prepared from sawdust by decoction method. The yellowish solution turns into dark brown colour indicating the formation of AgNPs. A sharp SPR (Surface Plasmon Resonance) band formation in UV-vis spectroscopy scan establishes the formation and stability of silver nanoparticles in an aqueous solution. SEM microphotograph indicated roughly spheroidal structure with (63±3) nm average diameters of newly synthesized AgNp. Polyvinyl alcohol (PVA) is eco-friendly and non-toxic to the environment was chosen for the preparation of polymeric matrix. The non-toxic concentration (1 ?g/mL) of AgNp was dispersed into PVA solution followed by cross-linked with maleic acid. PVA- maleic acid is cross-linked by the formation of an ester bond, whereas silver nanoparticles physically entrap into the cross-linked matrix. The silver nanoparticles were released from the matrix nearly after 10 min of swelling of the composite film. In a microbial assay using E. coli agar medium, PVA-AgNp composite film shows the significant killing of microorganisms. Microbial elimination is measured indirectly by pH measurement and dissolved oxygen concentration measurement of the effluent in situ against RO- water, taken as control. The dissolved oxygen concentration from RO water and effluent water was measured on Day “0” followed by treatment and incubation at the BOD chamber. The treatment with PVA-AgNp composite film reduced the BOD Level and increase dissolved oxygen level simultaneously increasing the quality of water.

O uso de checklist como estratégia para redução de pneumonia associada à ventilação mecânica em uma unidade de terapia intensiva adulto / Using a checklist as a strategy for the reduction of mechanical ventilator-associated pneumonia in an adult intensive care unit / El uso de una lista de verificación como estrategia para reducir la Neumonía Asociada a la Ventilación Mecánica en una unidad de cuidados intensivos para adultos

Objetivo: Avaliar a efetividade do instrumento fast-checklist, desenvolvido por uma equipe interdisciplinar como estratégia de redução de tempo de ventilação mecânica (VM) e pneumonia associada à ventilação mecânica (PAV) em uma unidade de terapia intensiva adulto. Métodos: Estudo quantitativo, longitudinal, observacional, realizado entre os meses de janeiro de 2018 e junho de 2019 em uma unidade de terapia intensiva adulto no Paraná. Os dados foram analisados pelo teste t-student. Resultados: Foram avaliados 759 internamentos, destes, 283 utilizaram VM. Os dados mostraram que antes do fast-checklist havia uma média de 3,22 casos de PAV, e após a instituição do instrumento, o valor reduziu significativamente para 0,33 (p=0,001); condição igualmente observado para os dias de VM. A média de VM era de 157 dias e passou para 133 (p=0,037) e a densidade de PAV era de 21,62 e passou para 2,82 (p=0,003). Através da análise do teste de t, dá para inferir uma redução dos casos de PAV de 4,9% ao mês. Conclusão: O uso de instrumentos como o checklist para redução de PAV, acompanhado da mudança de cultura e participação ativa de equipes interdisciplinares, são de extrema relevância na redução deste tipo de infecção e infecções relacionadas à assistência à saúde.(AU)

Objectives: To evaluate the effectiveness of using the Fast-Check List instrument developed by an interdisciplinary team as a strategy to reduce the time of mechanical ventilation (MV) and Mechanical Ventilator-associated Pneureamonia (VAP) in an Intensive Care Unit ­ Adult. Methods: Quantitative, longitudinal, observational study, carried out between the months of January 2018 and June 2019 in one adult Intensive Care Unit in Paraná. The data were analyzed by the T test. Results: 759 hospitalizations between January 2018 and June 2019 were evaluated, of these 283 used mechanical ventilation (VM). The data showed that before the Fast-CheckList there was an average of 3.22 VAP and after the institution of the instrument, the value significantly decreased to 0.33 (p = 0.001). Condition also observed for MV days. The mean MV was 157 days, and went to 133 (p = 0.037) and the VAP Density (DIPAV) was 21.62 and went to 2.82 (p = 0.003). Through the analysis of the t test, it is possible to infer a 4.9% month-on-month reduction in VAP cases. Conclusion: The use of instruments such as the checklist to reduce pneumonia associated with mechanical ventilation, accompanied by a change in culture and the active participation of interdisciplinary teams are extremely important in reducing this type of infection and infections related to healthcare.(AU)

Objetivos: Evaluar la efectividad del instrumento fast-checklist desarrollado por un equipo interdisciplinario como estrategia para reducir el tiempo de ventilación mecánica (VM) y la neumonía asociada con ventilación mecánica (PAV) en una Unidad de Cuidados Intensivos Adulta. Métodos: Estudio cuantitativo, longitudinal, observacional, realizado entre enero de 2018 y junio de 2019 en una unidad de cuidados intensivos para adultos en Paraná (Brasil). Los datos se analizaron mediante la prueba t student. Resultados: Se evaluaron 759 hospitalizaciones, de estas 283 utilizaron VM. Los datos mostraron que antes de la fast-checklist había un promedio de 3,22 casos de PAV y que después del uso del instrumento el valor disminuyó significativamente a 0,33 (p = 0,001). Esta condición también se observó para días de VM. El promedio de VM era de 157 días y pasó para 133 (p = 0,037) y la densidad de PAV que era de 21,62 pasó para 2,82 (p = 0,003). Por medio del análisis de la prueba t, es posible inferir una reducción de los casos de PAV de un 4,9% mes a mes. Conclusión: El uso de instrumentos como la lista de verificación para reducir la neumonía asociada con la ventilación mecánica, acompañado de un cambio en la cultura y la participación activa de equipos interdisciplinarios, son muy importantes para reducir este tipo de infección e infecciones relacionadas con la atención médica.(AU)

Effect of PVA-PEG Binders on Surface Roughness of Y-TZP Zirconia

@#Introduction: Y-TZP Zirconia is a ceramic used for dental implants because it has good biocompatibility and aesthetic properties, and it is affordable. Y-TZP formed from powder using uniaxial pressing with some added binder. The binders used are PVA, PEG and a combination of both. This combination reduce hardness and improve plasticity properties. Significantly increasing of the binder concentration and the surface roughness of the implant increases the porosity of the material as a place for the osseointegration process. Thus, the purpose of this study was to examine the different effect of PVA-PEG binders on the surface roughness of Y-TZP zirconia. Methods: Twelve samples were divided into three treatment groups: 100% PVA, 100% PEG and 4% PVA-PEG added to Y-TZP powder at a ratio of 95:5 (wt.%). The mixture was pressed using a uniaxial pressing machine, sintered and measured: the data was then analyzed using one-way ANOVA and Post Hoc LSD. Results: The result of the ANOVA showed that there were significant differences in the surface roughness of the Y-TZP with three different binders (P<0.05). The average surface roughness of the three binders are as follows: PVA 100% (0.8025±0.23472), PEG 100% (1.2325±0.23866), 4% of PVA-PEG (1.3450±0.27695). The LSD showed that there was significant differences between PVA 100% and PEG 100% (P<0.05), PVA 100% and 4% PVA-PEG (P<0.05). There was no significant difference between PEG 100% and 4% PVA-PEG (P>0.05). Conclusion: 4% PVA-PEG binders combination has effects on the surface roughness of Y-TZP zirconia

Evaluación de veinte años de Lignum-vitae (Guaiacum sanctum, Zygophyllaceae) en el Parque Nacional Palo Verde de Costa Rica

Introducción: El guayacán real (Guaiacum sanctum; Zygophyllaceae) de Mesoamérica y las Antillas está amenazado en gran parte de su área de distribución. Evaluamos si una población de G. sanctum en el Parque Nacional Palo Verde en Costa Rica es viable a largo plazo. Métodos Usando dos estudios demográficos, uno en 1997 y otro en 2017, estimamos las tasas de supervivencia y fecundidad para cada clase de edad, la tasa de crecimiento poblacional (lambda), y las elasticidades para cada tasa vital, y usamos un modelo determinístico denso-independiente para proyectar la trayectoria a largo plazo de la población. Resultados: Las tasas vitales estimadas durante los últimos 20 años sugieren que esta población está disminuyendo rápidamente, con un lambda estimado de 0.62. Aunque algunas clases de edad aumentaron en abundancias, los renovales son raros y los individuos reclutados en 1997 aún no alcanzaron la madurez reproductiva. Nuestros resultados sugieren que la abundancia actual de G. sanctum dentro del Parque Nacional podría no ser un buen indicador del estado de conservación a largo plazo, y por nuestro análisis de viabilidad poblacional, estimamos que la población estudiada disminuiría a menos del 1 % de su actual abundancia en los próximos 200 años. Conclusiones: El deterioro ecosistémico a escala de paisaje esta afectando la región del Parque Nacional Palo Verde, como la pérdida de dispersores de semillas y la supresión de alteraciones, podría compensar la protección pasiva de G. sanctum dentro de los límites del Parque Nacional. Confiar en la estricta protección dada por la locación de la población dentro del parque podría no ser suficiente para conservar esta población de G. sanctum. Recomendamos incorporar, dentro de un programa de investigación, una protección experimental más proactiva y/o medidas de restauración, posiblemente incluyendo tratamientos de alteraciones.

Introduction: The Lignum-vitae (Guaiacum sanctum; Zygophyllaceae) of Mesoamerica and the Greater Antilles, is threatened over much of its range. We evaluated whether a G. sanctum population in the Palo Verde National Park of Costa Rica is viable in the long term. Methods: Using two demographic studies, one in 1997 and the other in 2017, we estimated survival and fecundity rates for each tree age class, population growth rate (lambda), and vital rates elasticity, and we used a density-independent deterministic population model to project the long-term trend of that population. Results: The estimated vital rates during the last 20 years suggested that this population is rapidly decreasing. Although some age classes increased in abundance, seedlings are rare and the plants that recruited in 1997 have not yet reached reproductive maturity. Our results suggest that the current abundance of G. sanctum within the national park may not be a good indicator of its long-term conservation status, and from our population viability analysis, we estimated that the population we studied would decrease to less than 1 % of its current size within the next 200 years. Conclusions: Landscape-scale ecosystem deterioration affecting the greater PVNP region, such as loss of seed dispersers and suppression of disturbances, may offset the passive protection of G. sanctum within park boundaries. Relying on the overall strict protection afforded by the location of the population within the Palo Verde National Park may not be sufficient to conserve this population of G. sanctum. We recommend that more proactive experimental protection and/or restoration measures, possibly including disturbance treatments, be implemented within a research program.

Fabrication Of Nanofibres By Electrospinning Using Keratin From Waste Chicken Feathers, Pva And Agnps

Objective: To prepare and characterise keratin from chicken feathers (CF), collected from the slaughter house, and to blend with poly vinly alcohol (PVA) and biosynthesised silver nanoparticles (AgNPs) and to convert into nanofibers by an elctrospinning process. Methods: The extraction of keratin from chicken feathers was done by sodium m-bisulphite. The solution was subjected to ammonium sulphate precipitation to separate keratin. The nanoparticles was synthesised using tridax procumbens. The isolated keratin and PVA was mixed in the ration 0f 50:50 with 1 ml of biosynthesised nanoparticles was blended and made into nanofibres by electrospinning technique. Results: The precipitated protein was analysed using FT-IR analysis confirming the presence of β-keratin in the sample isolated from chicken feathers and the concentration of keratin was estimated to be 1.85 g/ml. PVA solution with 4% w/v had the best film forming ability. The solution containing keratin, PVA and silver nanoparticles was prepared in various proportions. These solutions when subjected to electrospinning, fibrous network was observed in 50:50 (PVA: Keratin) ratio with 1 ml of synthesised silver nanoparticle solution. Hydrogen bonding between keratin and PVA indicated in the XRD analysis showed successful film forming of the nanofiber, the DSC analysis also showed similar results as the obtained peak was at 214 °C which is in between the characteristic heat degradation temperature of both the keratin and PVA. The thermogravimetric analysis (TGA) showed high thermal stability as the complete degradation of the nanofiber was observed at 420 °C. Incorporation of metal nanoparticles by herbal approach using tridax procumbens in the nanofibers provided the antimicrobial properties. The nanofibres obtained by electrospinning process appeared stable and continous for solutions containing no more than 50% wt of CF. The average diameter of the nanofibres increased as the CF content increased. Conclusion: Keratin isolated from the waste chicken feathers impregnated with biosyntheised silver nanoparticles using tridax procumbens and PVA can be converted into nanofibers by electrospinning process. Thus, the biocomposite nano fibers are shown as a novel eco-friendly material that must be adequately applied in the development of green composites for the biomedical applications such as wound dressings.

Hidrogeis de polivinil-álcool (PVA) contendo o bacteriófago UFV-AREG1 para aplicação como curativo adesivo para a indústria de alimentos / Polyvinyl-alcohol (PVA) hydrogel containing the UFV-AREG1 bacteriophagus for application as a curative adhesive for the food industry

Infecções cutâneas obtidas por cortes nas mãos de manipuladores podem gerar contaminação nos alimentos. O objetivo deste trabalho foi incorporar o bacteriófago UFV-AREG1 em hidrogel de álcool poli(vinílico) – PVA, aplicando-o futuramente como curativo adesivo. Foi adicionado 1,0 mL de solução do fago no PVA e seco em estufa por 48 h. Após, os hidrogeis foram submetidos a testes de Intumescimento, Espectroscopia no infravermelho (FTIR) e efeito antimicrobiano sobre E. coli O157:H7. O intumescimento do PVA-fago foi maior que o PVA-controle (p<0,05). A área de inibição do PVA-fago foi de 3,715 cm2 contra 2,916 cm2 do controle. As análises do FTIR mostraram um pico para o PVA-fago não encontrado no PVA-controle. Foi possível incorporar o bacteriófago em hidrogel de PVA e avaliar sua liberação para posterior aplicação como curativo adesivo.

Caracterización de matrices de Polivinil alcohol-Alginato-Quitosano-Aloe vera / Characterization of Polyvinyl Alcohol-Alginate-Chitosan-Aloe Vera Matrix / Caracterização da Matriz de Polivinil Álcool-Alginato-Quitosana-Aloe Vera

Resumen El objetivo de este trabajo fue obtener un sistema que pueda ser usado para conservar de manera localizada en una herida dérmica las propiedades cicatrizantes y refrescantes del Aloe Vera usado en la medicina tradicional, integrando dicho principio activo en una matriz polimérica compuesta por alginato, quitosano y alcohol polivinílico (PVA), los cuales en conjunto poseen propiedades de resistencia mecánica, biodegradabilildad y biocompatibilidad, necesarios para este tipo de aplicación. Para llevar a cabo esta investigación, se evaluó la morfología, grupos funcionales, propiedades mecánicas y cinética de liberación de las muestras. Cada una de las matrices evidenciaron una morfología con poros interconectados y estabilidad mecánica. La liberación de Aloe vera desde la matriz de PVA-alginato-quitosano tuvo un comportamiento no fickiano, mientras la de alginato-quitosano siguió un comportamiento más cercano al fickiano. Las matrices de PVA-quitosano-alginato y alginato- quitosano por sus características, mecánicas, morfológicas de poros definidos e interconectados, y de cinética de liberación representan buenos modelos para ser tenidos en cuenta como sistemas de liberación controlada de medicamentos.

Abstract The purpose of this work was to obtain polymeric systems from Polyvinyl Alcohol (PVA), alginate and chitosan as possible matrix to encapsulate Aloe vera gel, seeking to integrate mechanical strength, biodegradability and biocompatibility of these polymers. In addition, Aloe vera gives the polymer matrix healing and emollient properties. Morphology, functional groups, mechanical properties and kinetic release behavior of the samples were evaluated. The matrices showed a morphology with interconnected pores and mechanical stability. The release of Aloe vera from the matrix of PVA-alginate-chitosan exhibited a non Fickian behavior, while alginate-chitosan presented a closer to Fickian behavior. PVA-chitosan-alginate and chitosan matrices, by their mechanical, morphological and interconnected and well defined pores, and alginate-release kinetics properties, represent good models to be taken into account as systems of controlled drug release.

Resumo O objetivo deste trabalho foi obter sistemas poliméricos a partir de Polivinil Álcool (PVA), alginato e quitosana como possíveis matrizes para encapsular o gel de Aloe vera, buscando integrar resistência mecânica, biodegradabilidade e biocompatibilidade desses polímeros. Além disso, a Aloe vera confere propriedades de cura e emoliência à matriz polimérica. Morfologia, grupos funcionais, propriedades mecânicas e comportamento de liberação cinética das amostras foram avaliados. As matrizes mostraram uma morfologia com poros interconectados e estabilidade mecânica. A liberação de Aloe vera a partir da matriz de PVA-alginato-quitosana exibiu um comportamento não Fickiano, enquanto alginato-quitosana apresentou um comportamento mais próximo ao Fickiano. As matrizes PVA-quitosana-alginato e quitosana, por seus poros mecânicos, morfológicos e interconectados e bem definidos, e as propriedades cinéticas de liberação de alginato, representam bons modelos a serem considerados como sistemas de liberação controlada do fármaco.

Research Progress of Polyvinyl Alcohol (PVA) Based on Hydrogel Dressings / 中国医疗器械杂志

This review introduces a brief description on the featured properties of polyvinyl alcohol based on hydrogel dressings. During past ten years many new artificial polymeric dressings have been developed, which meet requirements of wound healing. This review mainly focuses on one representative of ideal polymeric wound dressing membranes, polyvinyl alcohol based hydrogel dressings. But as the hydrogels with single component have low mechanical strength, recent trends have offered composite hydrogel membranes to achieve the ideal wound dressing requirements.

The efficacy of different embolic agents to block bronchial artery for massive hemoptysis secondary to bronchiectasis or pulmonary tuberculosis / 实用医学杂志

Objective To investigate the efficacy of gelatin sponge particles(GSP)or polyvinyl alcohol particles (PVA) for hemoptysis secondary to bronchiectasis or pulmonary tuberculosis. Methods The clinical data on 271 patients with bronchiectasis- or tuberculosis-induced hemoptysis were retrospectively analyzed. The efficacy and rates of recurrence and complications were analyzed. Results A total 271 patients were included in this study, 176 of whom suffered from bronchiectasis and the rest 95 had tuberculosis. One-week cure rate was signifi-cantly higher in bronchiectasis group than in tuberculosis group(73.3%vs. 46.3%,P0.05). No severe complications occurred. Conclusions In-terventional artery embolization therapy for hemoptysis secondary to bronchiectasis is better than tuberculosis-induced hemoptysis,and PVA is more effective than GSP. Recurrence of massive hemoptysis mostly occurrs within one month ,and most of the patients are complicated with blood supply and have a history of hemoptysis.

Study the release kinetics of curcumin released from PVA/curcumin composites and its evaluation towards hepatocarcinoma.

The polymer composites based on Polyvinyl alcohol loaded with different concentrations of commercial curcumin were prepared to be applied forcontrolled release drug delivery system to overcome the growth promotion of tumor cells. The prepared composites were subjected to drug release in aqueous media at room temperature. It was found that the amount of the released curcumin changed according to different pH media and the concentration of the loaded drug onto the polymer carrier. The diffusion coefficient of the released curcumin from the prepared composites was found to be 2.739X10-2, 1.638X10-2, and 5.777X10-4 in basic, acidic and neutral solution respectively according to Higuch's equation. The results of the in/vitro cytotoxic activity of the released curcumin showed sustained antiproliferative potency up to 30 % growth inhibition against the human liver cancer cell line (HEPG2) which extended to 25 days, to overcome hepatocarcinoma.

Facile way for synthesis silver nanoparticles for obtaining antibacterial textile fabrics.

One pot synthesis of silver nanoparticles (AgNPs) with well-defined size using polyvinyl alcohol (PVA) as stabilizing agent and sodium borohydride (NaBH4) as reducing agent was successfully performed. Preparation of AgNPs was carried out under a variety of conditions including concentrations of AgNPs, PVA and NaBH4. UV-vis spectra and TEM images were employed to characterize AgNPs obtained under the said different conditions. Physical and mechanical properties of cotton/polyester fabric treated with the synthesized silver nanoparticles were measured. SEM and EDX were used to scanning and observe the morphology and elemental change pertaining to fabric surface. Antibacterial activity against E. coli (Gm –ve bacteria) and Staphylococcus aureus (Gm +ve bacteria) were successfully examined against the treated and untreated fabrics.

Physical, Mechanical and Antimicrobial Evaluations of Physically Crosslinked PVA/Chitosan Hydrogels Containing Nanoparticles.

Chitosan/montmorillonite (MMT) and Poly vinyl Alcohol (PVA) / Silver nanoparticles (AgNPs) nanocomposites were prepared and formed hydrogel membranes using freeze thawing technique. The properties of the prepared hydrogels were investigated and compared to hydrogel membranes in presence and absence of nanometals. The physical behavior, mechanical properties and antibacterial activity was examined. Also the surface morphology monitored using scanning electron microscope. Antimicrobial activity against bacteria and yeast was also examined. The obtained results showed positive effect of nanometals especially AgNPs on swelling percent on the other hand tensile strength were combined by presence of MMT nanoparticles. The surface morphology showed homogenous images for all samples except samples containing MMT. All prepared samples containing nanoparticles showed antibacterial activity especially hydrogel membranes containing AgNPs.

Does adaptive strategy for delayed seed dispersion affect extinction probability of a desert species? an assessment using the population viability analysis and glass house experiment

Canopy seed bank is an important adaptive evolutionary trait that provides various types of protection to the seeds. However, costing of such evolutionary trait on plant survival is largely unknown. Present investigation provided a new insight on the serotonious habit of Blepharis sindica associated with its endangerment status. Extinction probabilities of two available population of B. sindica were quantified using two types of census data, i.e., fruiting body number and actual population size. Population Viability Analysis (PVA) revealed that delayed seed release tendency (higher fruiting body number) was not synchronized with actual ground conditions (lower population size). PVA analysis based on actual population size indicated that both the available populations would vanish within 20 years. The mean time of extinction calculated from both type census data indicated its extinction within 48 years. For assessing the conservation criteria, a glass house experiment was carried out with different soil types and compositions. Pure sand and higher proportions of sand -silt were more suitable compared to clay; further, gravelly surface was the most unsuitable habitat for this species. Collection of the seeds from mature fruits/capsule and their sowing with moderate moisture availability with sandy soil could be recommended.

Molecular dynamics simulation on mechanical properties of PVP/PVA / 医用生物力学

Objective To study the mechanical properties of PVP/PVA composite hydrogel and its interaction principle based on the molecular dynamics (MD) theory. Methods MD simulation was applied to investigate mechanical properties and radial distribution functions of PVP, PVA and their mixed system PVP/PVA. Results Compared with the pure PVP, mechanical properties of PVP/PVA were significantly improved, and not affected by temperature. The interaction between PVA and PVP was expected to occur through the interchain hydrogen bonding between the oxygen atom of PVP and the hydroxyl group of PVA. Conclusions MD method revealed the interaction mechanism of PVP/PVA hydrogel at molecular microscopic level and proved it better than pure PVP. Meanwhile, its mechanical properties were stable at different environment temperatures. These results provide a reliable theoretical research method for studying the fabrication process of hydrogel prosthesis in clinic and its mechanical properties.

Hexavalent chromium reduction by immobilized cells of Bacillus sphaericus AND 303

Bacillus sphaericus AND 303, a Cr(VI)-resistant and reducing bacterium reported from serpentine outcrops of Andaman was evaluated for Cr(VI) reduction using immobilized cells under batch culture. Screening of inert matrices for entrapment of whole cells indicated that polyvinyl alchohol-alginate was the most effective one reducing 87.5% of 20 µM Cr(VI) in 24 h. The rate of chromate reduction was dependent on initial Cr(VI) and biomass concentrations. The PVA cell beads were recycled three times without cell leakage and disintegration. The reduction efficiency was improved in the presence of glucose and glycerol as electron donors leading to complete reduction. However, the presence of additional metal ions was inhibitory to Cr(VI) reduction. It could be emphasized that PVA-alginate immobilized cells of B. sphaericus AND 303 could be used as a continuous bioprocess in treating Cr(VI) contaminated effluents.

Viabilidad poblacional de Alouatta palliata (Primates: Atelidae) y Cebus capucinus (Primates: Cebidae) en el Refugio de Vida Silvestre Privado Nogal, Sarapiquí, Heredia, Costa Rica / Population viability of Alouatta palliata (Primates: Atelidae) and Cebus capucinus (Primates: Cebidae) at Refugio de Vida Silvestre Privado Nogal, Sarapiquí, Heredia, Costa Rica

Population viability of Alouatta palliata (Primates: Atelidae) and Cebus capucinus (Primates: Cebidae) at Refugio de Vida Silvestre Privado Nogal, Sarapiquí, Heredia, Costa Rica. Habitat destruction may cause wildlife population fragmentation and is considered an important factor in small population species extinction. As wildlife populations become smaller, threats to their stability and persistence arise as a result of demographic, environmental and genetic stochastic factors. The aim of this work was to study the effects of population fragmentation on the long term viability of Alouatta palliata and Cebus capucinus populations, at Refugio de Vida Silvestre Privado Nogal, Sarapiquí (RVSPN), Heredia. For this we used the computer software VORTEX to run a population viability analysis (PVA) for both species. The input data of the PVA were taken from the demography structure of the RVSPN, literature sources from the species and from PVA related papers. We evaluated two sets of scenarios: small fragmented populations to reflect the population current state, and one larger and continuous population, to reflect the effect of reforestation actions followed by RVSPN to connect forest fragments. Results suggest that both A. palliata and C. capucinus can survive in isolated forest fragments. However, if different factors as inbreeding depression, catastrophes or habitat loss were incorporated to the scenarios, the small fragmented populations become unstable and the risk of extinction increased for both species. Continuous and larger populations were more robust against the threats incorporated in the scenarios when compared to the current situation of smaller and fragmented populations. The best management option for both species would be to continue reforestation efforts in the area to connect forest fragments, with the result of larger and continuous populations of both species. It is important to continue the observation of both species populations, and to promote a habitat management to reduce the negative effects of stochastic environmental events. Rev. Biol. Trop. 60 (2): 809-832. Epub 2012 June 01.

La destrucción del hábitat conlleva a la fragmentación de poblaciones de especies silvestres y se considera como uno de los principales factores en la extinción de especies A medida que las poblaciones se vuelven más pequeñas, surgen amenazas hacia su estabilidad y persistencia, como resultado de factores estocásticos demográficos, ambientales y genéticos. El objetivo de este trabajo fue estudiar los efectos de la fragmentación de poblaciones en la viabilidad de Alouatta palliata y Cebus capucinus en el Refugio de Vida Silvestre Privado Nogal (RVSPN), Sarapiquí, Heredia. Para esto se uso el programa VORTEX para correr un análisis de viabilidad de poblaciones (PVA) para ambas especies. La información utilizada en el PVA proviene de la estructura demográafica de las poblaciones del RVSPN, literatura sobre la historia natural de las especies y artículos relacionados con PVA. Los resultados sugieren que tanto A. palliata como C. capucinus pueden sobrevivir en fragmentos boscosos aislados. Sin embargo, si se incorporan factores como depresión por endogamia, catástrofes o perdida de hábitat, las pequeñas poblaciones fragmentadas se vuelven inestables y aumenta el riesgo de que desaparezcan. Las poblaciones continuas fueron más robustas ante las amenazas incorporadas, por lo que se recomienda continuar con la reforestación para unir los fragmentos boscosos. Es importante darle seguimiento a las poblaciones de ambas especies y tener un manejo de su hábitat para disminuir los efectos negativos de diferentes eventos estocásticos provocados por el ambiente.

Mechanical property analysis of PVA/HA composite hydrogel and its finite element simulation / 医用生物力学

Objective To study the effect from the content change in hydroxyapatite (HA) on mechanical properties of polyvinyl alcohol/hydroxyapatite(PVA/HA)composite hydrogel and its load bearing characteristics based on experiment and finite element simulation. Methods The compression and stress relaxation tests of PVA/HA composite hydrogel were performed on the UMT test machine. Through the simulation and experimental results, the load-bearing characteristics of PVA/HA composite hydrogel and the effect of HA on PVA/HA composite hydrogel performance were investigated. Results With HA content increasing, the compression modulus of PVA/HA composite hydrogel was first increased and then decreased, while its permeability coefficient was first decreased and then increased. When the HA content was 3%，the compression modulus of PVA/HA composite hy drogel reached maximum (1.25 MPa)and its permeability coefficient reached minimum(1.59×10-3 mm4•N-1•s-1). The fluid bearing proportion of PVA/HA composite hydrogel was first increased and then decreased with the loading time increasing, which presented a nonlinear change. The proportion of the fluid bearing was significantly increased after HA added into PVA / HA composite hydrogel. The stress relaxation rate was first increased and then decreased with HA content increasing. Under the same loaded displacement, PVA / HA composite hydrogel with 3% HA content could disperse more contact stress. Conclusions The internal bearing characteristics of PVA / HA composite hydrogel have a great impact on its mechanical properties. When the HA content is 3%, the PVA / HA composite hydrogel has the best mechanical properties, which are closer to those of the natural articular cartilage.

Interpenetrating polymer network of cross-linked blend microspheres for controlled release of Acebutolol HCl.

Carbohydrate polymeric blend microspheres consisting of chitosan (CS) and poly (vinyl alcohol) (PVA) were prepared by water-in-oil (W/O) emulsion method. These microspheres were crosslinked with glutaraldehyde and loaded with Acebutolol HCl, an anti hypertensive drug. The microspheres were characterized by Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), X-Ray diffraction (X-RD) and Scanning electron microscopy (SEM).The FTIR spectroscopy explains the crosslinking between the CS-PVA. DSC& X-RD indicated the molecular level distribution of Acebutolol HCl drug in the polymer matrix. The SEM of the microspheres suggested the formation of spherical particles. Swelling experiments on the microspheres provided important information on drug diffusion properties. Release data have been analyzed using an empirical equation to understand the nature of transport of drug containing solution through the polymeric matrices. The controlled release characteristic of the matrices for Acebutolol HCl was investigated in pH 7.4 media. The results indicate that the drug was released in a controlled manner up to 10 h.

Preparation and mechanical properties analysis of porous biological ceramics and PVA hydrogel composite material / 医用生物力学

Objective To cross-link the porous biological ceramics and PVA hydrogel to form a double layer construction between the artificial cartilage and hard joint, and to analyze its morphologies and mechanical properties. Methods With hydroxyl apatite (HA) as the substrate, the porous hydroxyl apatite biological ceramics with different porosities were prepared by using NH4HCO3 crystal grains as the pore-formed material. The poly vinyl alcohol (PVA) and epoxypropane were used as the primary material and cross-linking agent, respectively. The PVA hydrogel with double layer construction was cross-linked and prepared on the porous biological ceramics surface. The fracture appearances of the test specimen section were characterized. The performances of anti tensile strength and anti-shear strength for PVA hydrogel were analyzed. Results The cross-linked PVA hydrogel could permeate in the biological ceramics substrate, and the union between ceramic substrate and PVA hydrogel performed well. With the porosity of the porous biological ceramics increasing, the tension load and shear load of the PVA hydrogel samples both increased, and with the average porosity of 70%, the samples’ biggest tension load and shear load were 153.61 N and 64.46 N, respectively. But the corresponding tensile strength and shear strength both decreased and with the average porsity of 70%, the samples’ biggest tensile strength and shear strength were 2.12 MPa and 1.13 MPa, respectively. The failure mode of both tension and shear tests for PVA hydrogel samples was due to the crack propagation, and the fracture morphologies showed that obvious cracks and internal defects appeared on the fracture surface, while the source of the crack and the direction of the crack propagation could be observed. Conclusions Considering the compression strength of porous biological ceramics, the permeation effect on the porous biological ceramic substrate with the average porosity of 50% is moderate to be used, which ensures the appropriate shear and tensile strength of PVA hydrogel samples and the compression strength of porous biological ceramic.

Effect of new nucleus pulposus replacement on the flexibility motion and intradiscal pressure at the adjacent level / 医用生物力学

Objective To evaluate the biomechanical stability of pectin/polyvinyl alcohol composite （CoPP）hydrogel and to assess the range of motion(ROM) and intradiscal pressure (IDP) changes at the above adjacent segment after the anterior implantation of CoPP hydrogel and cage. Method Six fresh cadaveric lumbar spine specimens（L3～L5）were biomechanically tested on the robotic testing machine. ROM at L3/4 and L4/5 and intradiscal pressure at L3/4 were measured. All measurements were made with initially intact and followed by both CoPP and cage implantations. Results At the implanted level (L4/5), the CoPP spine showed no significant change in the other five motion directions except left lateral bending motion compared with the intact spine (P>0.05), whereas the cage spine decreased significantly in all motion directions when compared with the intact spine or CoPP spine (P0.05), whereas the ROM of cage spine significantly increased in all motion directions compared with the intact spine (P0.05). While the IDP of cage spine significantly increased in flexion/extension and left/right lateral bending compared with the intact spine or CoPP spine (P0.05). Conclusions The implantation of CoPP prosthetic nucleus can preserve the motion function at the operated level and maintain the lumbar stability. Compared with the lumbar fusion, the nucleus replacement has no significant effect on the ROM and IDP at adjacent level, which may decrease or avoid the adjacent segment degeneration.