An ultra scale-down analysis of the recovery by dead-end centrifugation of human cells for therapy.

An ultra scale-down method is described to determine the response of cells to recovery by dead-end (batch) centrifugation under commercially defined manufacturing conditions. The key variables studied are the cell suspension hold time prior to centrifugation, the relative centrifugal force (RCF), time of centrifugation, cell pellet resuspension velocities, and number of resuspension passes. The cell critical quality attributes studied are the cell membrane integrity and the presence of selected surface markers. Greater hold times and higher RCF values for longer spin times all led to the increased loss of cell membrane integrity. However, this loss was found to occur during intense cell resuspension rather than the preceding centrifugation stage. Controlled resuspension at low stress conditions below a possible critical stress point led to essentially complete cell recovery even at conditions of extreme centrifugation (e.g., RCF of 10000 g for 30 mins) and long (~2 h) holding times before centrifugation. The susceptibility to cell loss during resuspension under conditions of high stress depended on cell type and the age of cells before centrifugation and the level of matrix crosslinking within the cell pellet as determined by the presence of detachment enzymes or possibly the nature of the resuspension medium. Changes in cell surface markers were significant in some cases but to a lower extent than loss of cell membrane integrity. Biotechnol. Bioeng. 2015;112: 997-1011. © 2014 Wiley Periodicals, Inc

Ultrafine aerosol generation from free falling nanopowders : experiments and numerical modelling

In the last few years, the interest on nanomaterials and their applications have increased in a considerable way. Hence, the knowledge of the possible hazards on human health becomes necessary. Besides the description of the toxicological effects of nanomaterials, the exposure level on the worksites is one of the key data of the problem. The present work aims at studying the resuspension of ultrafine particles in the air during the falling of nanostructured powders. A numerical approach has been developed aiming at simulating the free falling of a powder cluster. The results show that a resuspension of particles occurs following the powder cluster deformation during the free fall of the particles in the air. Isolated particles remain suspended in the air for a long time

Quantifying measures to limit wind driven resuspension of sediments for improvement of the ecological quality in some shallow Dutch lakes

Although phosphorus loadings are considered the main pressure for most shallow lakes, wind-driven resuspension can cause additional problems for these aquatic ecosystems. We quantified the potential effectiveness of measures to reduce the contribution of resuspended sediments, resulting from wind action, to the overall light attenuation for three comparable shallow peat lakes with poor ecological status in the Netherlands: Loosdrecht, Nieuwkoop, and Reeuwijk (1.8–2.7 m depth, 1.6–2.5 km fetch). These measures are: 1. wave reducing barriers, 2. water level fluctuations, 3. capping of the sediment with sand, and 4. combinations of above. Critical shear stress of the sediments for resuspension (Vcrit), size distribution, and optical properties of the suspended material were quantified in the field (June 2009) and laboratory. Water quality monitoring data (2002–2009) showed that light attenuation by organic suspended matter in all lakes is high. Spatial modeling of the impact of these measures showed that in Lake Loosdrecht limiting wave action can have significant effects (reductions from 6% exceedance to 2% exceedance of Vcrit), whereas in Lake Nieuwkoop and Lake Reeuwijk this is less effective. The depth distribution and shape of Lake Nieuwkoop and Lake Reeuwijk limit the role of wind-driven resuspension in the total suspended matter concentration. Although the lakes are similar in general appearance (origin, size, and depth range) measures suitable to improve their ecological status differ. This calls for care when defining the programme of measures to improve the ecological status of a specific lake based on experience from other lakes.

Particle size distribution of suspended solids in the Chesapeake Bay entrance and adjacent shelf waters

Characteristics of suspended solids, including total suspended matter, total suspended inorganics, total suspended organics, particle size distribution, and the presence of the ten most prominent particle types were determined. Four research vessels simultaneously collected samples along four transects. Samples were collected within a 2-hour period that coincided with the maximum ebb penetration of Chesapeake Bay outwelling. The distribution of primary and secondary particle size modes indicate the presence of a surface or near-surface plume, possibly associated with three sources: (1) runoff, (2) resuspension of material within the Bay, and/or (3) resuspension of material in the area of shoals at the Bay mouth. Additional supportive evidence for this conclusion is illustrated with ocean color scanner data

Environmental hazard assessment of a marine mine tailings deposit site and potential implications for deep-sea mining

Portmán Bay is a heavily contaminated area resulting from decades of metal mine tailings disposal, and is considered a suitable shallow-water analogue to investigate the potential ecotoxicological impact of deep-sea mining. Resuspension plumes were artificially created by removing the top layer of the mine tailings deposit by bottom trawling. Mussels were deployed at three sites: i) off the mine tailings deposit area; ii) on the mine tailings deposit beyond the influence from the resuspension plumes; iii) under the influence of the artificially generated resuspension plumes. Surface sediment samples were collected at the same sites for metal analysis and ecotoxicity assessment. Metal concentrations and a battery of biomarkers (oxidative stress, metal exposure, biotransformation and oxidative damage) were measured in different mussel tissues. The environmental hazard posed by the resuspension plumes was investigated by a quantitative weight of evidence (WOE) model that integrated all the data. The resuspension of sediments loaded with metal mine tails demonstrated that chemical contaminants were released by trawling subsequently inducing ecotoxicological impact in mussels' health. Considering as sediment quality guidelines (SQGs) those indicated in Spanish action level B for the disposal of dredged material at sea, the WOE model indicates that the hazard is slight off the mine tailings deposit, moderate on the mine tailings deposit without the influence from the resuspension plumes, and major under the influence of the resuspension plumes. Portmán Bay mine tailings deposit is a by-product of sulphide mining, and despite differences in environmental setting, it can reflect the potential ecotoxic effects to marine fauna from the impact of resuspension of plumes created by deep-sea mining of polymetallic sulphides. A similar approach as in this study could be applied in other areas affected by sediment resuspension and for testing future deep-sea mining sites in order to assess the associated environmental hazards.info:eu-repo/semantics/publishedVersio

Wind induced resuspension in a shallow tropical lagoon (GBR)

In shallow environments, particle resuspension can induce large ecological effects. Under some certain conditions of fetch, wind velocity, bathymetry and bed roughness, resuspension is generated by wind induced waves. During December 1991, a shallow station (1 m depth) in the north shore of a tropical lagoon (Côte d'Ivoire) was investigated in order to study the impact of wind induced resuspension on the ecosystem. In this area, Austral trade winds are dominant almost all year long, and their velocity shows a marked diel pattern. During the survey, three sequences were distinguished : a period of Austral trade winds (with possible resuspension), a period of Borela trade winds. Only Austral trade winds with a speed > 3 m s-1 allowed particle resuspension. For chlorophyll, mineral seston and ammonia, significantly higher values were noted during the windy sequences. Conductivity and water colour varied in relation to tides. Granulometric and mineralogical analyses showed that only the 0-3 cm superficial level of the sediment was involved in resuspension. (D'après résumé d'auteur

Sediment resuspension as a water quality regulator in lakes

Sediment resuspension, the return of the bottom material into the water column, is an important process that can have various effects on a lake ecosystem. Resuspension caused by wind-induced wave disturbance, currents, turbulent fluctuations and bioturbation affects water quality characteristics such as turbidity, light conditions, and concentrations of suspended solids (SS) and nutrients. Resuspension-mediated increase in turbidity may favour the dominance of phytoplankton over macrophytes. The predator-prey interactions contributing to the trophic state of a lake may also be influenced by increasing turbidity. Directly, the trophic state of a lake can be influenced by the effect of sediment resuspension on nutrient cycling. Resuspension enhances especially the cycling of phosphorus by bringing the sedimentary nutrients back into the water column and may thereby induce switches between phosphorus and nitrogen limitation. The contribution of sediment resuspension to gross sedimentation, turbidity, and concentration of SS and nutrients was studied in a small, deep lake as well as in a multibasin lake with deep and shallow areas. The effect of ice cover on sediment resuspension and thereby on phosphorus concentrations was also studied. The rates of gross sedimentation and resuspen¬sion were estimated with sediment traps and the associations between SS and nutrients were considered. Sediment resuspension, caused by wind activity, comprised most of the gross sedimenta¬tion and strongly contributed to the concentration of SS and turbidity in the lakes studied. Additionally, via the influence on SS, resuspension affected the concentration of total phosphorus (TP) and soluble reactive phosphorus (SRP), as well as the total nitrogen to total phosphorus (TN:TP) ratio. Although contrasting results concerning the dependence between the SS and SRP concentrations were observed, it could be concluded that sediment resuspension during strong algal blooms (pH > 9) led to aerobic release of P. The main findings of this thesis were that in the course of the growing season, sediment resuspension coupled with phytoplankton succession led to liberation of P from resuspended particles, which in turn resulted in high TP concentrations and low TN:TP ratios. This development was likely a cause of strong cyanobacterial blooms in midsummer.Järven pohjaan laskeutunut aines, pohjasedimentti, voi sekoittua uudelleen vesimassaan aallokon, erilaisten virtausten ja eliöiden (kalat, pohjaeläimet) vaikutuksesta. Ilmiöllä, jota kutustaan sedimentin resuspendoitumiseksi, voi olla merkittäviä vaikutuksia järviekosysteemiin. Sedimentin sekoittuminen vesimassaan vaikuttaa esimerkiksi veden ravinnepitoisuuksiin sekä kiintoainepitoisuuden ja sameuden nousun kautta valaistusolosuhteisiin. Valaistusolosuhteiden muuttuminen saattaa johtaa leväbiomassan lisääntymiseen vesikasvillisuuden kustannuksella. Myös näön perusteella saalistavien eliöiden ravinnonhankinta voi vaikeutua sameuden kasvaessa. Sedimentin resuspensio vaikuttaa usein myös vesistöjen tärkeän perusravinteen, fosforin kiertoon ja sillä on näin ollen rehevöitymistä edistävä vaikutus. Tämän väitöskirjan osajulkaisuissa tutkittiin kahden eri järven sedimentaatiota (aineksen laskeutumista vesipatsaassa) sekä sedimentin resuspension vaikutusta jär¬vien veden sameuteen, kiintoainepitoisuuteen ja ravinnepitoisuuksiin. Yhdessä osajulkaisussa tutkittiin myös jääpeitteen vaikutusta resuspensioon ja järven fosforipitoisuuksiin. Tutkimusten mukaan suurin osa järvien sedimentaatiosta muodostui sedimentin resuspensiosta. Resuspensiolla oli myös selkeä vaikutus järvien kiintoainepitoisuuksiin ja sameuteen. Kiintoainepitoisuuksien nousu vaikutti lisäksi voimakkaasti ravinnepitoisuuksiin (fosfori, typpi, typpi:fosfori-suhde). Tutkimuksen merkittävin tulos oli, että sedimentin sekoittuessa vesipatsaaseen matalassa ja rehevässä järvessä voimakkaiden leväkukintojen aikaan, sedimenttipartikkeleista vapautui fosforia levien käyttöön. Tämä nosti veden kokonaisfosforipitoisuuksia ja laski typpi:fosfori-suhdetta. Kyseinen kehityskulku oli todennäköisesti keskikesällä havaittujen runsaiden sinileväkukintojen syy. Tutkimuksen tulokset osoittavat myös, että matalassa tuulille alttiissa järvessä sedimentin resuspension aiheuttama ravinnekuormitus voi olla monikertainen ulkoiseen kuormitukseen (jokien tuomat ravinteet) nähden. Toisaalta vähäinenkin ulkoinen kuormitus on tällaisissa järvissä merkittävää, koska kerran järveen joutuneet ravinteet jäävät voimakkaan resuspension johdosta pitkäksi aikaa biologiseen kiertoon

Influence of hydrodynamic processes on the fate of sedimentary organic matter on continental margins

Understanding the effects of hydrodynamic forcing on organic matter (OM) composition is important for assessment of organic carbon (OC) burial in marginal seas on regional and global scales. Here we examine the relationships between regional oceanographic conditions (bottom shear stress), and the physical characteristics (mineral surface area and grain size) and geochemical properties (OC content [OC%] and carbon isotope compositions [13C, 14C]) of a large suite of surface sediments from the Chinese marginal seas to assess the influence of hydrodynamic processes on the fate of OM on shallow continental shelves. Our results suggest that 14C content is primarily controlled by organo‐mineral interactions and hydrodynamically driven resuspension processes, highlighted by (i) positive correlations between 14C content and OC% (and surface area) and (ii) negative correlations between 14C content and grain size (and bottom shear stress). Hydrodynamic processes influence 14C content due to both OC aging during lateral transport and accompanying selective degradation of OM associated with sediment (re) mobilization, these effects being superimposed on the original 14C characteristics of carbon source. Our observations support the hypotheses of Blair and Aller (2012, https://doi.org/10.1146/annurev‐marine‐120709‐142717) and Leithold et al. (2016, https://doi.org/10.1016/j.earscirev.2015.10.011) that hydrodynamically driven sediment translocation results in greater OC 14C depletion in broad, shallow marginal seas common to passive margin settings than on active margins. On a global scale, this may influence the extent to which continental margins act as net carbon sources and sinks. Our findings thus suggest that hydrodynamic processes are important in shaping the nature, dynamics, and magnitude of OC export and burial in passive marginal seas