Durability assessment of polymer trileaflet heart valves

The durability of a polymer trileaflet valve is dependent on leaflet stress concentrations, so valve designs that reduce stress can, hypothetically, increase durability. Design aspects that are believed to contribute to reduced leaflet stress include stent flexibility, parabolic coaptation curvature, and leaflet anisotropy. With this in mind, the purpose of this investigation was to elucidate what specific combinations of these parameters promote optimal acute and long-term valve function. A combination of four stent designs, seven leaflet reinforcement materials, and three coaptation geometries were evaluated through a combination of experimentation and modeling. Static tensile and Poisson’s ratio tests and dynamic tensile fatigue testing were used to evaluate the individual leaflet components; and hydrodynamic testing and accelerated valve fatigue was used to assess complete valve prototypes. The two most successful designs included a 0.40 mm thick knit-reinforced valve with a fatigue life of 10.35 years, and a 0.20 mm thick knit-reinforced valve with a 28.9 mmHg decrease in pressure drop over the former. A finite element model was incorporated to verify the impact of the above-mentioned parameters on leaflet stress concentrations. Leaflet anisotropy had a large impact on stress concentrations, and matching the circumferential modulus to that of the natural valve showed the greatest benefit. Varying the radial modulus had minimal impact. Varying coaptation geometry had no impact, but stent flexibility did have a marked effect on the stress at the top of the commissure, where a completely rigid stent resulted in a higher peak stress than a flexible stent (E = 385 MPa). In conclusion, stent flexibility and leaflet anisotropy do effect stress concentrations in the SIBS trileaflet valve, but coaptation geometry does not. Regions of high stress concentrations were linked to failure locations in vitro, so a fatigue prediction model was developed from the S/N curves generated during dynamic tensile testing of the 0.20 mm knit-reinforced leaflets. Failure was predicted at approximately 400 million cycles (10 years) at the top of the commissure. In vitro fatigue of this valve showed failure initiation after approximately 167 million cycles (4.18 years), but it was related to a design defect that is subsequently being changed.

Durability Assessment of Polymer Trileaflet Heart Valves

The durability of a polymer trileaflet valve is dependent on leaflet stress concentrations, so valve designs that reduce stress can, hypothetically, increase durability. Design aspects that are believed to contribute to reduced leaflet stress include stent flexibility, parabolic coaptation curvature, and leaflet anisotropy. With this in mind, the purpose of this investigation was to elucidate what specific combinations of these parameters promote optimal acute and long-term valve function. A combination of four stent designs, seven leaflet reinforcement materials, and three coaptation geometries were evaluated through a combination of experimentation and modeling. Static tensile and Poisson’s ratio tests and dynamic tensile fatigue testing were used to evaluate the individual leaflet components; and hydrodynamic testing and accelerated valve fatigue was used to assess complete valve prototypes. The two most successful designs included a 0.40 mm thick knit-reinforced valve with a fatigue life of 10.35 years, and a 0.20 mm thick knit-reinforced valve with a 28.9 mmHg decrease in pressure drop over the former. A finite element model was incorporated to verify the impact of the above-mentioned parameters on leaflet stress concentrations. Leaflet anisotropy had a large impact on stress concentrations, and matching the circumferential modulus to that of the natural valve showed the greatest benefit. Varying the radial modulus had minimal impact. Varying coaptation geometry had no impact, but stent flexibility did have a marked effect on the stress at the top of the commissure, where a completely rigid stent resulted in a higher peak stress than a flexible stent (E = 385 MPa). In conclusion, stent flexibility and leaflet anisotropy do effect stress concentrations in the SIBS trileaflet valve, but coaptation geometry does not. Regions of high stress concentrations were linked to failure locations in vitro, so a fatigue prediction model was developed from the S/N curves generated during dynamic tensile testing of the 0.20 mm knit-reinforced leaflets. Failure was predicted at approximately 400 million cycles (10 years) at the top of the commissure. In vitro fatigue of this valve showed failure initiation after approximately 167 million cycles (4.18 years), but it was related to a design defect that is subsequently being changed.

Physical oceanography, sea-bed photographs and videos of benthos from the Weddell Sea taken with remote operated vehicle CHEROKEE during POLARSTERN cruise ANT-XXIII/8

The marine ecosystem on the eastern shelf of the Antarctic Peninsula was surveyed 5 and 12 years after the climate-induced collapse of the Larsen A and B ice shelves. An impoverished benthic fauna was discovered, that included deep-sea species presumed to be remnants from ice-covered conditions. The current structure of various ecosystem components appears to result from extremely different response rates to the change from an oligotrophic sub-ice-shelf ecosystem to a productive shelf ecosystem. Meiobenthic communities remained impoverished only inside the embayments. On local scales, macro- and mega-epibenthic diversity was generally low, with pioneer species and typical Antarctic megabenthic shelf species interspersed. Antarctic Minke whales and seals utilised the Larsen A/B area to feed on presumably newly established krill and pelagic fish biomass. Ecosystem impacts also extended well beyond the zone of ice-shelf collapse, with areas of high benthic disturbance resulting from scour by icebergs discharged from the Larsen embayments.

Supercapattery based on binder-free Co3 (PO4)2·8H2O multilayer nano/microflakes on nickel foam

A binder-free cobalt phosphate hydrate (Co3(PO4)2·8H2O) multilayer nano/microflake structure is synthesized on nickel foam (NF) via a facile hydrothermal process. Four different concentrations (2.5, 5, 10, and 20 mM) of Co2+ and PO4–3 were used to obtain different mass loading of cobalt phosphate on the nickel foam. The Co3(PO4)2·8H2O modified NF electrode (2.5 mM) shows a maximum specific capacity of 868.3 C g–1 (capacitance of 1578.7 F g–1) at a current density of 5 mA cm–2 and remains as high as 566.3 C g–1 (1029.5 F g–1) at 50 mA cm–2 in 1 M NaOH. A supercapattery assembled using Co3(PO4)2·8H2O/NF as the positive electrode and activated carbon/NF as the negative electrode delivers a gravimetric capacitance of 111.2 F g–1 (volumetric capacitance of 4.44 F cm–3). Furthermore, the device offers a high specific energy of 29.29 Wh kg–1 (energy density of 1.17 mWh cm–3) and a specific power of 4687 W kg–1 (power density of 187.5 mW cm–3).

Effects of hypercapnia on aspects of feeding, nutrition, and growth in the edible sea urchin Lytechinus variegatus held in culture

Land-based aquaculture facilities experience occasional hypercapnic conditions due to the accumulation of the metabolic waste product carbon dioxide. Pre-gonadal Lytechinus variegatus (horizontal diameter=20 mm) were exposed to control (608 µatm pCO2, pH 8.1) or hypercapnic conditions (1738 µatm pCO2, pH 7.7) in synthetic seawater for 14 weeks. Sea urchins exposed to hypercapnic conditions exhibited significantly slower growth (reduced dry matter production), primarily due to reduced test production. Higher fecal production rates and lower ash absorption efficiency (%) in individuals exposed to hypercapnic conditions suggest the ability to process or retain dietary carbonates may have been affected. Significant increases in neutral lipid storage in the gut and increased soluble protein storage in the gonads of individuals exposed to hypercapnic conditions suggest alterations in nutrient metabolism and storage. Furthermore, organic production and energy allocation increased in the lantern of those individuals exposed to hypercapnic conditions. These results suggest chronic exposure to hypercapnic conditions alters nutrient allocation to organ systems and functions, leading to changes in somatic and reproductive production.

(Table 1) Stable carbon isotope ratios of methane and carbon dioxide from ODP Leg 169S holes

Sites 1033 and 1034 of ODP Leg 169S in Saanich Inlet have an unusual diagenetic system, that has the appearance of being depth reversed, i.e. a bacterial methane accumulation zone underlain by a sulphate reduction zone. During the late Pleistocene grey, undifferentiated, glacio-marine clays were deposited with low Corg contents (<0.4 wt.%), and interstitial fluids replete in SO4 (ca. 27 mM), devoid of CH4 and low in nutrients. This indicates oxic conditions are present, reflecting the open exchange of waters with Haro Strait during the Pleistocene before the Saanich Peninsula emerged. In the earliest Holocene (ca. 11,000 years BP) the inlet was formed, severely restricting water circulation, and leading to the presence of anoxic bottom waters. The sediments are laminated and show a dramatic rise to high Corg, Norg and Stot contents (up to 2.5, 0.4, 1.4 wt.%, respectively) over a period of ca. 1000 years. The nutrient concentrations are especially high (TA, NH4, PO4 up to 115 meq/l, 20 mM and 400 µM, respectively), SO4 is exhausted and CH4 is prolific. Stable carbon isotope ratio measurements of CH4 and co-existing CO2 indicate that methanogenesis is via carbonate reduction (delta13C-CH4 ca. -60 to - 70 per mil, delta13C-CO2 ca. +10 per mil). At the sulphate-methane interfaces, both at the near-surface and at 50 mbsf (Site 1033) and 80 mbsf (Site 1034) methane consumption by sulphate reducing bacteria is intensive.

Abundance of calcareous dinoflagellates of sediment cores from the South Atlantic Ocean

Despite the increasing interest in the South Atlantic Ocean as a key area of the heat exchange between the southern and the northern hemisphere, information about its palaeoceanographic conditions during transitions from glacial to interglacial stages, the so-called Terminations, are not well understood. Herein we attempt to increase this information by studying the calcareous dinoflagellate cysts and the shells of Thoracosphaera heimii (calcareous cysts) of five Late Quaternary South Atlantic Ocean cores. Extremely high accumulation rates of calcareous cysts at the Terminations might be due to a combined effect of increased cyst production and better preservation as result of calm, oligotrophic conditions in the upper water layers. Low relative abundance of Sphaerodinella albatrosiana compared with Sphaerodinella tuberosa in the Cape Basin may be the result of the relatively colder environmental conditions in this region compared with the equatorial Atlantic Ocean with high relative abundance of S. albatrosiana. Furthermore, the predominance of S. tuberosa during glacials and interglacials at the observed site of the western Atlantic Ocean reflects decreased salinity in the upper water layer.

(Table 1, page 119) 10Be and 9Be concentrations in manganese nodules of the Pacific Ocean

The usefulness of cosmogenic beryllium-10 (half life = 2.5 Ma) for studying the rates of accumulation of ferromanganese nodules is reported based on its measured depth distribution in the top 20 mm of these deposits. Accumulation rates have been obtained in the range of 1 to 4 mm/Ma, which are in good agreement with rates determined using the 230Th method on the same nodules. The use of 10Be offers promise in extending the dating to the outer few cm of the nodules. This contrasts with conventional methods using 230Th and 231Pa isotopes which, due to their comparatively short half lives, are limited to a few mm at the surface of the nodules. Detailed studies of 10Be in the manganese deposits coupled with other trace element analyses should prove valuable in understanding the processes of formation of these deposits and the chronology of events recorded by them.

Phytoplanktonic microfossil groups of sediments from the South and Equatorial Atlantic

Individual planktonic microfossil species, or assemblage groups of different species, are often used to, qualitatively and/or quantitatively, reconstruct past (sub)surface-water conditions of the world's oceans and seas. Until now, little information has been available on the surface sediment distribution patterns and paleoenvironmental reconstruction potential of coccolith, calcareous dinoflagellate cyst and organic-walled dinoflagellate cyst assemblages of the South and equatorial Atlantic, especially at the species level. This paper (i) summarizes the distributions of these three phytoplanktonic microfossil groups in numerous Atlantic surface sediments from 20°N-50°S and 30°E-65°W and determines their relationship with the physicochemical and trophic conditions of the overlying (sub)surface-waters, and (ii) determines the synecology of the three phytoplankton groups by carrying out statistical analyses (i.e. detrended and canonical correspondence analyses) on all groups simultaneously. Ecological relationships are additionally strengthened by statistically comparing the distribution patterns of the phytoplankton groups with those of planktonic foraminifera (Pflaumann et al. 1996; Niebler et al. 1998), as the ecological preferences of the latter are much better known. Many of the analyzed phytoplanktonic microfossil species or groups of species in the surface sediments do show restricted distributions which primarily reflect the environmental conditions of the upper water masses above them (e.g. sea-surface temperature, productivity, stratification). The acquired 'reference' data sets are large and diverse enough to allow future development of transfer functions for the reconstruction of past surface-water conditions, and show that there is still an enormous paleoenvironmental reconstruction potential concealed in many fossil coccolith and dinoflagellate cyst assemblages.

Dinámica superficial del agua en planicies semiáridas : el papel de las precipitaciones y de la cobertura vegetal

El balance de agua de ecosistemas situados sobre planicies áridas y semiáridas se encuentra determinado por la precipitación (principal entrada de agua) y la evapotranspiración (principal salida de agua). La fracción de la precipitación que ingresa en el suelo y su redistribución espacial son los principales controles del funcionamiento de dichos ecosistemas, como por ejemplo de su productividad primaria neta. En esta tesis se exploró la dinámica superficial del agua en planicies semiáridas dedicadas a la ganadería extensiva, evaluando el papel de las precipitaciones y de la cobertura vegetal a distintas escalas espaciales. En el centro de Argentina, la distribución relativa de tamaño de eventos de precipitación resultó constante en el espacio (sitios dispuestos a lo largo de un gradiente de precipitación de ~1000 mm/año) y en el tiempo (50 años); encontrándose que el 10 por ciento de los eventos de precipitación de mayor tamaño explicó casi la mitad de la precipitación anual. El reemplazo de bosques secos nativos por pasturas en el Chaco Árido, por un lado, aumentó la evaporación potencial del suelo y el escurrimiento superficial a escala de parcela (~1 ha); por otro lado, redujo a la mitad la conductividad hidráulica saturada y generó una reducción de la variabilidad espacial del agua del suelo a escala de parche (0,25 m2). La intensidad de los eventos de precipitación resultó el factor determinante para explicar los procesos de redistribución de agua del suelo de los bosques secos nativos; parches menos vegetados capturaron más agua en eventos de precipitación poco intensos (mayor a 10 mm/h), mientras que parches más vegetados capturaron más agua en eventos más intensos ((menor a 20 mm/h). La cosecha de agua de lluvia en represas o tajamares representó menos del 1 por ciento de la precipitación anual, desempeñando un papel menor en el balance de agua regional (~20000 km2); sin embargo, a escala de parcela o lote (1-100 ha) puede afectar profundamente la partición de flujos de agua, por ejemplo generando recarga inducida como resultado de las pérdidas por infiltración de las represas. Los resultados obtenidos en esta tesis aportan nuevas perspectivas para entender la dinámica superficial del agua en sistemas ganaderos semiáridos, y por lo tanto, para mejorar la producción primaria y secundaria de los mismos.

Dinoflagelados (Peridiniales, Prorocentrales) do microplâncton na plataforma continental e talude do extremo sul do Brasil (inverno 2005, verão 2007)

This study aimed at identifying morpho-species of microplankton dinoflagellates (> 20 μm) of the order Peridiniales and Prorocentrales off Santa Marta Grande Cape, CSMG (SC, 28º 40’ S) and Albardão-Chui, AC ( r S, 34º 40’ S) during oceanographic cruises conducted in winter 2005 and summer 2007. Plankton samples were obtained by vertical net (mesh size 20 μm) hauls preserved with formaldehyde 4% and analyzed using the inverted microscope equipped with a digital camera. The identification of Peridiniales species was based on the number and morphology of thecal plates enhanced with Calco Fluor White M r 2 whenever necessary and the identification of Prorocentrales was based on cell size, shape, presence of apical processes, pore pattern and marks at the intercalary band. We identified 25 species, including Protoperidinium (11), Prorocentrum (6), Corythodinium (3), Podolampas (2), Oxytoxum (2) and Heterocapsa (1). Prorocentrum species were widely distributed on the continental shelf of southern Brazil, while Peridiniales species were mainly found off Albardão-Chui during winter, especially under the influence of the plume of La Plata River. Oxytoxum milneri was the first time recorded in southern Brazil, while Protoperidinium cassum var. cassum , P. curtipes and Heterocapsa triquetra , were first registered in Brazil.

First observation on neustonic plastics in waters off NW Spain (spring 2013 and 2014)

This paper examines the presence and distribution of plastic particles in waters off the NW Spanish Atlantic coast. A pilot sampling program was initiated in 2013 to study the presence of plastic particles in surface waters. A total of 41 neuston samples were collected using a manta trawl fitted with a 333 μm mesh (21 samples in 2013 and 20 samples in 2014). Several types of plastic particles were observed in 95% of the stations. A total of 1463 plastic microparticles (<5 mm; mps) and 208 mesoparticles (>5 mm and <20 mm; MPS) were counted. Average concentrations recorded were 0.034 ± 0.032 and 0.176 ± 0.278 mps m−2 and 0.005 ± 0.005 and 0.028 ± 0.043 MPS m−2, respectively for 2013 and 2014. Results on this emerging topic are discussed as a preliminary step towards implementation of the Marine Strategy Framework Directive in the region. Harmonization of protocols for determination of plastic particles is urgently needed in order to compare results between regions and to ensure coherence in the implementation of the MSFD. This aspect is also important at a worldwide scale.

Quantifying nitrous oxide emissions from sugarcane cropping systems : Optimum sampling time and frequency

Nitrous oxide (N2O) emissions from soil are often measured using the manual static chamber method. Manual gas sampling is labour intensive, so a minimal sampling frequency that maintains the accuracy of measurements would be desirable. However, the high temporal (diurnal, daily and seasonal) variabilities of N2O emissions can compromise the accuracy of measurements if not addressed adequately when formulating a sampling schedule. Assessments of sampling strategies to date have focussed on relatively low emission systems with high episodicity, where a small number of the highest emission peaks can be critically important in the measurement of whole season cumulative emissions. Using year-long, automated sub-daily N2O measurements from three fertilised sugarcane fields, we undertook an evaluation of the optimum gas sampling strategies in high emission systems with relatively long emission episodes. The results indicated that sampling in the morning between 09:00–12:00, when soil temperature was generally close to the daily average, best approximated the daily mean N2O emission within 4–7% of the ‘actual’ daily emissions measured by automated sampling. Weekly sampling with biweekly sampling for one week after >20 mm of rainfall was the recommended sampling regime. It resulted in no extreme (>20%) deviations from the ‘actuals’, had a high probability of estimating the annual cumulative emissions within 10% precision, with practicable sampling numbers in comparison to other sampling regimes. This provides robust and useful guidance for manual gas sampling in sugarcane cropping systems, although further adjustments by the operators in terms of expected measurement accuracy and resource availability are encouraged. By implementing these sampling strategies together, labour inputs and errors in measured cumulative N2O emissions can be minimised. Further research is needed to quantify the spatial variability of N2O emissions within sugarcane cropping and to develop techniques for effectively addressing both spatial and temporal variabilities simultaneously.

Refolding of omega conotoxin peptide derived from marine snail, Conus magus, to evaluate its analgesic effects

Oxidative refolding is one of the key challenges hampering the development of peptide based compounds as therapeutics. The correct refolding for three disulfide peptide like w-Conotoxi n MVIIA is difficult and crucial for biological activity. This work advanced knowledge of chemical and biological for improve oxidative refolding of synthetic w-Conotoxi n MVIIA in base of Conus magus venom. The present study aimed to set up an appropriate and effective protocols for refolding of disulfide-rich w-Conotoxin MVIIA. In this study, the crude peptide was protected with Acm group, according to the right amino acid sequences (Synthesized by Australian Company). The crude peptide was purified by H PLC. To prepare the peptide to refolding, innovative deprotection applied molar ratio (AMR) method was performed based on mercury. Accuracy of deprotection was approved by reverse phase chromatography. The deprotected target peptide (omega-conotoxin) was determined by SDS-PAGE. Then the Oxidative refolding of target peptide was performed in six protocol based on Guanidinium chloride and oxidized and reduced Glutathione. Analgesic effect of refolded peptide was surveyed with formalin test in mice Balb/c. Non neurotoxic effects of target peptides were survey with ICV injection in mice model (C57/BL6). The innovative deprotection protocol performed based on the best ratio of mercury/2-mercaptoethanol adjusted to 1mg/10p1 in 90 minute. The results showed the yield and purity of omega-conotoxin MVIIA as 93 and 95%, respectively. Refolding of 40 mg omega Conotoxin with GSSG and GSH on ratio of 10:1 and 20 mM ammonium acetate showed the best analgesic effect compared with the other methods. The result showed 95.5% yield and 98% purity of omega-conotoxin MVIIA in this refolding method. Related refolding method reduced 85% pain in experimented mice using 7 ng of the peptide. That was 71.5 fold stronger than morphine and 2 times than standard Prialt®. And it was not neurotoxic in mice. In this study, refolding method for omega-conotoxin MVIIA was optimized in the fourth factor including: reducing the time, amount and number of reagent and increase the efficiency. We introduced new method for deprotection of omega-conotoxin MVIIA. Effective, economic and applied refolding and deprotecti on method was performed in this research may al so be applied to similar omega conotoxin peptides.

In vitro technique for selecting onion FOR white rot disease- resistance

In vitro selection is one of the most effective and efficient techniques for plant improvement. This is due to its ability to isolate plants with the desired character(s), either by applying a selection agent on the culture media to drive the selection of somaclones with the required character(s), or by establishing particular conditions that change in the genomes of somaclones toward the required character. The objective of this study was to identify a suitable protocol for in vitro selection of Allium white rot disease ( Sclerotium cepivorum ) tolerance in commercial Egyptian onion varieties, namely Giza 20, Giza 6 and Beheri Red. Oxalic acid (OA), the phytotoxin produced by Sclerotium cepivorum, was used as the selective agent. Seeds of the three Egyptian varieties were germinated on four concentrations (0.0, 0.02, 0.2, 2 and 20 mM) of Oxalic acid. Among the tested cultivars, Beheri Red had the highest germination frequency (52%) at all concentrations tested, followed by Giza 20 (42.6%), and Giza 6 at (32%). Cotyledon explants from the varieties were cultured on toxic MSBDK medium, supplemented with 0, 3, 6 and 12 mM OA. The survival of calli on MSBDK free toxic medium was 70.7% for all tested cultivars; however, MSBDK-stressed medium, with 3 mM OA reduced the viable calli to 42.1%. The highest OA concentration (12 mM) completely inhibited calli induction from cotyledons explants. A medium supplement with 3 mM OA retarded 80% of calli growth. Among 156 tested calli of Beheri Red, only 23 calli (14.7%) survived on toxic medium for 45 days. Similarly, there was 15.6% survival for Giza 20 calli, while 40.1% of the Giza 6 calli survived. Plantlets were regenerated from surviving calli and transplanted onto ex vitro, and formed bulb after acclimatisation.