Topographically induced self-deformation of the nuclei of cells: dependence on cell type and proposed mechanisms

Osteosarcoma-derived cell lines (SaOs-2, MG63) have recently been shown to deform their nucleus considerably in response to surface topography. Such a deformation had not been described previously. Here we present results on additional cell lines, including cancerous (OHS4, U2OS), immortalized (F/STRO-1⁺A and FHSO6) and healthy cells (HOP). The cancerous cells were found to deform extensively, the immortalized cells showed small deformations, whereas the healthy cells showed deformation only at short incubation times. These results suggest a strong link between the malignant transformation of cells and the state of the cytoskeletal network. We propose mechanisms to explain the deformation in which the cytoskeleton either pushes down on the nucleus during spreading or pulls it down upon adhesion to the pillars.     

Surface Oxidation as a Cause of High Open‐Circuit Voltage in CdSe ETA Solar Cells

TiO₂/CdSe/CuSCN extremely thin absorber (ETA) solar cells are found to give relatively high values of open‐circuit voltage (>0.8 V) but low currents upon annealing the cadmium selenide (CdSe) in air (500 ºC). Annealing in N₂ produces much lower photovoltages and slightly lower photocurrents. Band structure measurements show differences between the two annealing regimes that, however, appear to favor the N₂‐annealed CdSe. On the other hand, chemically resolved electrical measurements (CREM) of the cells reveal marked differences in photo‐induced charge trapping, in particular at absorber grain boundaries of the air versus N₂‐annealed systems, correlated with the formation of Cd–O species at the CdSe surface. Using transient absorption and photovoltage decay, pronounced lifetime differences are also observed, in agreement with the strong suppression of charge recombination. The results point to a multiple role of grain surface‐oxidation, which both impedes electron injection from the CdSe to the TiO_2, but, much more significantly, enhances hole injection to the CuSCN via passivation of hole traps that act as efficient recombination centers.     

Bioluminescent Optogenetics: A Novel Experimental Therapy to Promote Axon Regeneration after Peripheral Nerve Injury

Functional recovery after peripheral nerve injury (PNI) is poor, mainly due to the slow and incomplete regeneration of injured axons. Experimental therapies that increase the excitability of the injured axons have proven remarkably successful in promoting regeneration, but their clinical applicability has been limited. Bioluminescent optogenetics (BL-OG) uses luminopsins, fusion proteins of light-generating luciferase and light-sensing ion channels that could be used to increase neuronal excitability if exposed to a suitable substrate. Excitatory luminopsins were expressed in motoneurons of transgenic mice and in wildtype mice transduced with adeno-associated viral vectors. Intraperitoneal administration of coelenterazine (CTZ), a known luciferase substrate, generated intense bioluminescence in peripheral axons. This bioluminescence increased motoneuron excitability. A single administration of CTZ immediately after sciatic nerve transection and repair markedly enhanced motor axon regeneration. Compound muscle action potentials were 3–4 times larger than controls by 4 weeks after injury. The results observed with transgenic mice were comparable to those of mice in which the luminopsin was expressed using viral vectors. Significantly more motoneurons had successfully reinnervated muscle targets four weeks after nerve injury in BL-OG treated mice than in controls. Bioluminescent optogenetics is a promising therapeutic approach to enhancing axon regeneration after PNI.     

Protective Effects of a Hyaluronan-Binding Peptide (P15-1) on Mesenchymal Stem Cells in an Inflammatory Environment

Mesenchymal stem cells (MSCs) obtained from various sources, including bone marrow, have been proposed as a therapeutic strategy for the improvement of tissue repair/regeneration, including the repair of cartilage defects or lesions. Often the highly inflammatory environment after injury or during diseases, however, greatly diminishes the therapeutic and reparative effectiveness of MSCs. Therefore, the identification of novel factors that can protect MSCs against an inflammatory environment may enhance the effectiveness of these cells in repairing tissues, such as articular cartilage. In this study, we investigated whether a peptide (P15-1) that binds to hyaluronan (HA), a major component of the extracellular matrix of cartilage, protects bone-marrow-derived MSCs (BMSCs) in an inflammatory environment. The results showed that P15-1 reduced the mRNA levels of catabolic and inflammatory markers in interleukin-1beta (IL-1β)-treated human BMSCs. In addition, P15-1 enhanced the attachment of BMSCs to HA-coated tissue culture dishes and stimulated the chondrogenic differentiation of the multipotential murine C3H/10T1/2 MSC line in a micromass culture. In conclusion, our findings suggest that P15-1 may increase the capacity of BMSCs to repair cartilage via the protection of these cells in an inflammatory environment and the stimulation of their attachment to an HA-containing matrix and chondrogenic differentiation.     

CO2 hydrate composite for ocean carbon sequestration

Rapid CO2 hydrate formation was investigated with the objective of producing a negatively buoyant CO2-seawater mixture under high-pressure and low-temperature conditions, simulating direct CO2 injection at intermediate ocean depths of 1.0-1.3 km. A coflow reactor was developed to maximize CO2 hydrate production by injecting water droplets (e.g., approximately 267 microm average diameter) from a capillary tube into liquid CO2. The droplets were injected in the mixing zone of the reactor where CO2 hydrate formed at the surface of the water droplets. The water-encased hydrate particles aggregated in the liquid CO2, producing a paste-like composite containing CO2 hydrate, liquid CO2, and water phases. This composite was extruded into ambient water from the coflow reactor as a coherent cylindrical mass, approximately 6 mm in diameter, which broke into pieces 5-10 cm long. Both modeling and experiments demonstrated that conversion from liquid CO2 to CO2 hydrate increased with water flow rate, ambient pressure, and residence time and decreased with CO2 flow rate. Increased mixing intensity, as expressed by the Reynolds number, enhanced the mass transfer and increased the conversion of liquid CO2 into CO2 hydrate. Using a plume model, we show that hydrate composite particles (for a CO2 loading of 1000 kg/s and 0.25 hydrate conversion) will dissolve and sink through a total depth of 350 m. This suggests significantly better CO2 dispersal and potentially reduced environmental impacts than would be possible by simply discharging positively buoyant liquid CO2 droplets. Further studies are needed to address hydrate conversion efficiency, scale-up criteria, sequestration longevity, and impact on the ocean biota before in-situ production of sinking CO2 hydrate composite can be applied to oceanic CO2 storage and sequestration.     

Transformation of calcium cyanamide and its inhibitory effect on urea nitrification in some tropical soils

Transformation of calcium cyanamide and its inhibitory effect on urea nitrification was studied in some tropical soils. Three soils, from Onne, Mokwa and Samaru, representing different agro-climatological zones of Nigeria were incubated with calcium cyanamide, urea or a mixture of both for eight weeks at 30 °C and at field capacity moisture content. The recovery of inorganic N (NH ₄ ⁺ plus NO ₂ ^- plus NO ₃ ^- )from calcium cyanamide varied from 64% to 87% in different soils. Most of the inorganic N accumulated was in NH ₄ ⁺ form. Nitrification of the accumulated NH ₄ ⁺ in all the soils was slow.Urea (75 mg N kg^–1 soil) was completely nitrified within a week in the Samaru and Mokwa soils whereas in the Onne soil the rate of nitrification was slow. Addition of CaCN₂ at the rate of 10 mg N kg^–1 soil generally delayed ammonification of urea and nitrification was severely inhibited in all the soils. Addition of CaCN₂ at the rate of 20 mg N kg^–1 soil further reduced the ammonification of urea and completely inhibited the nitrification. High recovery of inorganic N from calcium cyanamide and its effective reduction of nitrification of urea make it suitable source of N for plants in the tropics, provided it is managed to avoid phyto-toxicity.     

Sustaining Reforms in Water Service Delivery: the Role of Service Quality,Salience, Trust and Financial Viability

Water Resources Management - The long-term success of water service reforms depends on sufficient revenues being collected from users to allow access to be extended and quality of service to be...     

Towards standardisation of proof load testing: pilot test on viaduct Zijlweg

Proof load tests of bridges can be very useful for structures with a lack of information, or for structures of which the effect of material degradation is difficult to assess. Contrary to diagnostic load testing, proof load testing is not well-defined in current standards in terms of required load and analysis of measurements. The risk related to the high loads used in proof load testing requires standardisation for these tests. The paper highlights important considerations for proof load testing that may lead to the development of guidelines in the Netherlands, by illustrating a pilot study on the viaduct Zijlweg in the Netherlands. This reinforced concrete bridge rates too low in shear. Topics of interest are the required load that the bridge has to withstand to be approved by the load test and the interpretation of the measurements during the test to avoid permanent damage to the structure. These measurements were compared to the stop criteria from existing codes for buildings, to examine if recommendations for the use with bridges can be formulated. The final result of the test on this case study is that the capacity of the viaduct is proven to be sufficient for shear and bending moment.