Vitrification is the most sought after route to the cryopreservation of animal embryos and oocytes and other cells of medical, genetic, and agricultural importance. Current thinking is that ...successful vitrification requires that cells be suspended in and permeated by high concentrations of protective solutes and that they be cooled at very high rates to below −100°C. We report here that neither of these beliefs holds for mouse oocytes. Rather, we find that if mouse oocytes are suspended in media that produce considerable osmotic dehydration before vitrification and are subsequently warmed at ultra high rates (10,000,000°C/min) achieved by a laser pulse, nearly 100% will survive even when cooled rather slowly and when the concentration of solutes in the medium is only 1/3rd of standard.
Climate change has increased the incidence of coral bleaching events, resulting in the loss of ecosystem function and biodiversity on reefs around the world. As reef degradation accelerates, the need ...for innovative restoration tools has become acute. Despite past successes with ultra-low temperature storage of coral sperm to conserve genetic diversity, cryopreservation of larvae has remained elusive due to their large volume, membrane complexity, and sensitivity to chilling injury. Here we show for the first time that coral larvae can survive cryopreservation and resume swimming after warming. Vitrification in a 3.5 M cryoprotectant solution (10% v/v propylene glycol, 5% v/v dimethyl sulfoxide, and 1 M trehalose in phosphate buffered saline) followed by warming at a rate of approximately 4,500,000 °C/min with an infrared laser resulted in up to 43% survival of Fungia scutaria larvae on day 2 post-fertilization. Surviving larvae swam and continued to develop for at least 12 hours after laser-warming. This technology will enable biobanking of coral larvae to secure biodiversity, and, if managed in a high-throughput manner where millions of larvae in a species are frozen at one time, could become an invaluable research and conservation tool to help restore and diversify wild reef habitats.
Predicting debris flow runout is of major importance for hazard mitigation. Apart from topography and volume, runout distance and area depends on debris flow composition and rheology, but how is ...poorly understood. We experimentally investigated effects of composition on debris flow runout, depositional mechanisms, and deposit geometry. The small‐scale experimental debris flows were largely similar to natural debris flows in terms of flow behavior, deposit morphology, grain size sorting, channel width‐depth ratio, and runout. Deposit geometry (lobe thickness and width) in our experimental debris flows is largely determined by composition, while the effects of initial conditions of topography (i.e., outflow plain slope and channel slope and width) and volume are negligible. We find a clear optimum in the relations of runout with coarse‐material fraction and clay fraction. Increasing coarse‐material concentration leads to larger runout. However, excess coarse material results in a large accumulation of coarse debris at the flow front and enhances diffusivity, increasing frontal friction and decreasing runout. Increasing clay content initially enhances runout, but too much clay leads to very viscous flows, reducing runout. Runout increases with channel slope and width, outflow plain slope, debris flow volume, and water fraction. These results imply that debris flow runout depends at least as much on composition as on topography. This study improves understanding of the effects of debris flow composition on runout and may aid future debris flow hazard assessments.
Key Points
There is an optimum debris flow composition for maximum runout
Debris flow runout depends at least as much on composition as on topography
Deposit geometry is largely controlled by debris flow composition
We report additional details of the thermal modeling, selection of the laser, and construction of the Cryo Jig used for our ultra-rapid warming studies of mouse oocytes (Jin et al., 2014). A Nd:YAG ...laser operating at 1064nm was selected to deliver short 1ms pulses of sufficient power to produce a warming rate of 1×107°C/min from −190°C to 0°C. A special Cryo Jig was designed and built to rapidly remove the sample from LN2 and expose it to the laser pulse. India ink carbon black particles were required to increase the laser energy absorption of the sample. The thermal model reported here is more general than that previously reported. The modeling reveals that the maximum warming rate achievable via external warming across the cell membrane is proportional to (1/R2) where R is the cell radius.
Deltas and estuaries worldwide face the challenge of capturing sufficient sediment to keep up with relative sea‐level rise. Knowledge about sediment pathways and fluxes is crucial to combat adverse ...effects on channel morphology, for example, erosion which enhances bank collapse and increasing tidal penetration. Here, we construct sediment budgets which quantify annual changes for the urbanized Rhine‐Meuse Delta of the Netherlands, a typical urban delta experiences changing fluvial and coastal fluxes of sediment, engineering works and dredging and dumping activities. The delta shows a negative sediment budget (more outgoing than incoming sediment) since the 1980s, due to anthropogenic intervention. Following a large offshore port expansion, dredging in ports and harbors in the region has doubled in the past 5 years, likely due to the induced change in net sediment fluxes. In addition, the deeper navigation channels, ports, and harbors are now trapping siltier sediment, changing the sediment composition in the mouth. The removal of sediment by dredging is adverse to the necessity for sediment in heavily eroding branches. To allow for sustainable sediment management in the future and to cope with sea‐level rise, further measurements are required to properly quantify the amount of incoming sediment at the boundaries of the system and the internal mechanisms of transport. The varied response of the branches has important consequences for navigation, ecology and flood safety and management of the sediment in the system. These effects will be of pivotal importance in coming decades with similar implications for many urbanized deltas worldwide.
Plain Language Summary
Deltas need sufficient sediment to grow with sea‐level rise and counteract natural and human‐induced subsidence. A sediment budget quantifies if a delta is net gaining sediment or if it is losing sediment over a long time period. The Rhine‐Meuse Delta (RMD) has a negative budget: Its entire network of channels is losing sediment annually. The reason for this negative budget is the high amounts of sand and mud removed for navigation to inland ports and from harbors which are periodically dredged. As a result, some of the channels in the area degrade rapidly, which causes issues for river management and dynamics including water quality, flood safety, and ecology. Other deltas worldwide are managed similarly to the RMD and will therefore face the same sediment issues. A strategy is required to deal with channel degradation and find ways to maintain sediment in the system.
Key Points
Human impacts on delta channels can be quantified using empirical relations between tidal prism and cross‐section area in delta channels
Establishing sediment budgets for delta channel networks requires data concerning both sand and mud, which are jointly subject to dredging
Reduced sediment input to deltas may partially be compensated for by influx of marine sediment, which is a large source of uncertainty
The analysis of experiments for the purpose of determining cell membrane permeability parameters is often done using the Kedem–Katchalsky (KK) formalism (1958). In this formalism, three parameters, ...the hydraulic conductivity (Lp), the solute permeability (Ps), and a reflection coefficient (ς), are used to characterize the membrane. Sigma was introduced to characterize flux interactions when water and solute (cryoprotectant) cross the membrane through a common channel. However, the recent discovery and characterization of water channels (aquaporins) in biological membranes reveals that aquaporins are highly selective for water and do not typically cotransport cryoprotectants. In this circumstance, sigma is a superfluous parameter, as pointed out by Kedem and Katchalsky. When sigma is unneeded, a two-parameter model (2P) utilizing onlyLpandPsis sufficient, simpler to implement, and less prone to spurious results. In this paper we demonstrate that the 2P and KK formalism yield essentially the same result (LpandPs) when cotransporting channels are absent. This demonstration is accomplished using simulation techniques to compare the transport response of a model cell using a KK or 2P formalism. Sigma is often misunderstood, even when its use is appropriate. It is discussed extensively here and several simulations are used to illustrate and clarify its meaning. We also discuss the phenomenological nature of transport parameters in many experiments, especially when both bilayer and channel transport are present.
PDF
