Search Results (9)

Sodium alanate (NaAlH₄) is a prospective H₂ storage material for stationary and mobile applications, as NaAlH₄ contains 7.4 wt% of H₂, and it is possible to do multiple H₂ release and accumulation cycles. Nanoconfinement is a potential solution to enhance the H₂ release properties of NaAlH₄. To optimize the supporting material and the synthesis method used for the nanoconfinement of NaAlH₄, a better understanding of the influence of nanoconfinement on the H₂ release processes is necessary. Thus, the H₂ release from bulk, purely nanoconfined, and intermediate NaAlH₄ is measured at different temperature ramp rates, and the characteristic parameters for each hydrogen release process are determined. Activation energies for each process are determined using the Kissinger method, and the effect of nanoconfinement on the activation energies is analysed. The impact of nanoconfinement on the H₂ release processes from NaAlH₄ and the limitations of each process in case of bulk and nanoconfined NaAlH₄ are presented and discussed. Nanoconfinement of NaAlH₄ decreases activation energies of the initial reversible H₂ release steps to between 30 and 45 kJ mol⁻¹ and increased the activation energy of the last irreversible H₂ release step to over 210 kJ mol⁻¹. Full article

Material from the electric arc furnace smelting of municipal solid waste incineration (MSWI) bottom ash was easily converted into highly porous glass-ceramics by a combination of inorganic gel casting and sinter-crystallization at 1000 °C. In particular, the gelation of aqueous suspensions of fine glass powders, transformed into “green” foams by intensive mechanical stirring, occurred with a limited addition of alkali activator (1 M NaOH). The products coupled the stabilization of pollutants with good mechanical properties (e.g., compressive strength approaching 4 MPa). Interestingly, they could be used also as raw material for new glass-ceramic foams, obtained by the same gel casting and sintering method, with no degradation of chemical stability. Limitations in the crushing strength, derived from the limited viscous flow densification of semi-crystalline powders, were overcome by mixing powders from recycled foams with 30 wt% soda-lime glass. The new products finally featured an even higher strength-to-density ratio than the foams from the first cycle. Full article

Cast-in anchor channels are used to connect steel components to concrete structures e.g., for elevators, cranes or machines, where repeated load cycles require verification against fatigue failure. The fatigue resistance of anchor channels may be determined by tests according to the interactive method, which provides a complete description of the S/N curve from one to infinite load cycles according to the current assessment document. This procedure differs from conventional fatigue concepts, which do not consider loads that are part of low cycle fatigue, but also question the general existence of an endurance limit. An alternative approach presented in this paper is based on the assumption that the S/N curve can be approximated by a bilinear function. The procedure for the evaluation of fatigue tests on anchor channels embedded in concrete is described. A comparison with the current qualification criteria is given by a test example to discuss the applicability of the proposed method. Full article

K-ion batteries (KIBs) have emerged as an auspicious alternative to Li-ion batteries (LIBs) owing to their uniform distribution, plentiful reserves, the low cost of K resources, and their similar physicochemical properties to Li resources. The development of KIBs is seriously limited by cathode materials. Here, a hybrid of K₃V₂(PO₄)₃ (KVP) particles triple-coated by amorphous carbon, carbon nanotubes (CNTs), and reduced graphene oxide (rGO) nanosheets (KVP/C/CNT/rGO) was fabricated by a facile ball milling process followed by heat treatment. Consequently, a stable capacity of 57 mAh g⁻¹ can be achieved at 0.2C, and a slow capacity decaying rate (0.06% per cycle) is displayed during 500 cycles under a high current density of 5C. The remarkable reversible capacity and excellent long-term cycling life are mainly due to the enhanced interwoven C/CNT/rGO networks and superior KVP crystal structure stability, which can provide multi-channel for fast electron transport and effective K⁺ diffusion. Full article

An overview was made to understand the regulation system of a bacterial cell such as Escherichia coli in response to nutrient limitation such as carbon, nitrogen, phosphate, sulfur, ion sources, and environmental stresses such as oxidative stress, acid shock, heat shock, and solvent stresses. It is quite important to understand how the cell detects environmental signals, integrate such information, and how the cell system is regulated. As for catabolite regulation, F1,6B P (FDP), PEP, and PYR play important roles in enzyme level regulation together with transcriptional regulation by such transcription factors as Cra, Fis, CsrA, and cAMP-Crp. αKG plays an important role in the coordinated control between carbon (C)- and nitrogen (N)-limitations, where αKG inhibits enzyme I (EI) of phosphotransferase system (PTS), thus regulating the glucose uptake rate in accordance with N level. As such, multiple regulation systems are co-ordinated for the cell synthesis and energy generation against nutrient limitations and environmental stresses. As for oxidative stress, the TCA cycle both generates and scavenges the reactive oxygen species (ROSs), where NADPH produced at ICDH and the oxidative pentose phosphate pathways play an important role in coping with oxidative stress. Solvent resistant mechanism was also considered for the stresses caused by biofuels and biochemicals production in the cell. Full article

We used the NASA Ocean Biogeochemical Model (NOBM) combined with remote sensing data via assimilation to evaluate the contribution of four phytoplankton groups to the total primary production. First, we assessed the contribution of each phytoplankton groups to the total primary production at a global scale for the period 1998–2011. Globally, diatoms contributed the most to the total phytoplankton production (~50%, the equivalent of ~20 PgC∙y⁻¹). Coccolithophores and chlorophytes each contributed ~20% (~7 PgC∙y⁻¹) of the total primary production and cyanobacteria represented about 10% (~4 PgC∙y⁻¹) of the total primary production. Primary production by diatoms was highest in the high latitudes (>40°) and in major upwelling systems (Equatorial Pacific and Benguela system). We then assessed interannual variability of this group-specific primary production over the period 1998–2011. Globally the annual relative contribution of each phytoplankton groups to the total primary production varied by maximum 4% (1–2 PgC∙y⁻¹). We assessed the effects of climate variability on group-specific primary production using global (i.e., Multivariate El Niño Index, MEI) and “regional” climate indices (e.g., Southern Annular Mode (SAM), Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO)). Most interannual variability occurred in the Equatorial Pacific and was associated with climate variability as indicated by significant correlation (p < 0.05) between the MEI and the group-specific primary production from all groups except coccolithophores. In the Atlantic, climate variability as indicated by NAO was significantly correlated to the primary production of 2 out of the 4 groups in the North Central Atlantic (diatoms/cyanobacteria) and in the North Atlantic (chlorophytes and coccolithophores). We found that climate variability as indicated by SAM had only a limited effect on group-specific primary production in the Southern Ocean. These results provide a modeling and data assimilation perspective to phytoplankton partitioning of primary production and contribute to our understanding of the dynamics of the carbon cycle in the oceans at a global scale. Full article

The finitely repeated Prisoners’ Dilemma is a good illustration of the discrepancy between the strategic behaviour suggested by a game-theoretic analysis and the behaviour often observed among human players, where cooperation is maintained through most of the game. A game-theoretic reasoning based on backward induction eliminates strategies step by step until defection from the first round is the only remaining choice, reflecting the Nash equilibrium of the game. We investigate the Nash equilibrium solution for two different sets of strategies in an evolutionary context, using replicator-mutation dynamics. The first set consists of conditional cooperators, up to a certain round, while the second set in addition to these contains two strategy types that react differently on the first round action: The ”Convincer” strategies insist with two rounds of initial cooperation, trying to establish more cooperative play in the game, while the ”Follower” strategies, although being first round defectors, have the capability to respond to an invite in the first round. For both of these strategy sets, iterated elimination of strategies shows that the only Nash equilibria are given by defection from the first round. We show that the evolutionary dynamics of the first set is always characterised by a stable fixed point, corresponding to the Nash equilibrium, if the mutation rate is sufficiently small (but still positive). The second strategy set is numerically investigated, and we find that there are regions of parameter space where fixed points become unstable and the dynamics exhibits cycles of different strategy compositions. The results indicate that, even in the limit of very small mutation rate, the replicator-mutation dynamics does not necessarily bring the system with Convincers and Followers to the fixed point corresponding to the Nash equilibrium of the game. We also perform a detailed analysis of how the evolutionary behaviour depends on payoffs, game length, and mutation rate. Full article

In this perspective, we discuss the cytoplasm in actively growing bacterial cells contrasted with viable but nonculturable (VBNC) cells. Actively growing bacterial cells contain a more molecularly crowded and organized cytoplasm, and are capable of completing their cell cycle resulting in cell division. In contrast, nutrient starving bacteria in the physiological VBNC state are struggling to survive, as essential nutrients are not available or limiting. The cytoplasm is not as molecularly crowded as gene expression is minimal (e.g., ribosome, transcript, tRNA and protein numbers are decreased), energy pools are depleted, cells may exhibit leakage, and DNA is not being replicated for cell division. Full article

Certain applications of passive radio frequency identification (RFID), such as those in healthcare where the patient’s name, identification or medical record must be stored, require data within a tag to be encrypted. Encrypted data within an RFID tag has the potential to affect the accuracy or time to read/write the data by the reader. The current research measures and analyzes the effects of encryption, distance of read and delay time between two read/write cycles on the accuracy of the read or write function in an RFID infrastructure. The research also measures and evaluates the time to read/write (R/W) data that is encrypted and compares this encrypted data with unencrypted data.The data encryption standard (DES) encryption method is used in this research due to the limitation of the tag. A multi-functional interface has been developed for the user to test the performance using a High Frequency RFID reader. The measurements were repeated 1000 times for each R/W test.The performance of R/W accuracy is not affected in any meaningful way by encryption even though there is an increase in memory requirement from 88 bytes to 128 bytes. The effect of R/W distance shows that the performance decreases with increase in the distance between the reader and the tag.By inserting a small amount of delay time between different cycles, we can get a significant increase up to 100% accuracy for read function. However, the write accuracy is not affected as significantly as the read accuracy.The effect of the encryption on the time to write the data on the tag shows that encrypted data group takes 70 ~ 120 milliseconds for the transmission more than the unencrypted data group.We conclude that while the encryption does not have a significant impact on the accuracy of R/W, the distance and cycle delay does. Also, the encrypted data takes longer to write to the tag. Full article