No abstract

Glycogen synthase kinase-3 (GSK3) has been implicated in major neurological disorders, but its role in normal neuronal function is largely unknown. Here we show that GSK3beta mediates an interaction between two major forms of synaptic plasticity in the brain, N-methyl-D-aspartate (NMDA) receptor-dependent long-term potentiation (LTP) and NMDA receptor-dependent long-term depression (LTD). In rat hippocampal slices, GSK3beta inhibitors block the induction of LTD. Furthermore, the activity of GSK3beta is enhanced during LTD via activation of PP1. Conversely, following the induction of LTP, there is inhibition of GSK3beta activity. This regulation of GSK3beta during LTP involves activation of NMDA receptors and the PI3K-Akt pathway and disrupts the ability of synapses to undergo LTD for up to 1 hr. We conclude that the regulation of GSK3beta activity provides a powerful mechanism to preserve information encoded during LTP from erasure by subsequent LTD, perhaps thereby permitting the initial consolidation of learnt information.

In existing experiments it is known that the slow evolution of nonlinear deep-water waves exhibits certain asymmetric features. For example, an initially symmetric wave packet of sufficiently large wave slope will first lean forward and then split into new groups in an asymmetrical manner, and, in a long wavetrain, unstable sideband disturbances can grow unequally to cause an apparent downshift of carrier-wave frequency. These features lie beyond the realm of applicability of the celebrated cubic Schrödinger equation (CSE), but can be, and to some extent have been, predicted by weakly nonlinear theories that are not limited to slowly modulated waves (i.e. waves with a narrow spectral band). Alternatively, one may employ the fourth-order equations of Dysthe (1979), which are limited to narrow-banded waves but can nevertheless be solved more easily by a pseudospectral numerical method. Here we report the numerical simulation of three cases with a view to comparing with certain recent experiments and to complement the numerical results obtained by others from the more general equations.

No abstract

Dynamic transfer functions for two cavitating inducers of the same geometry but different size are presented, compared, and discussed. The transfer functions for each inducer indicate similar trends as the cavitation number is decreased. The nondimensional results for the two sizes are compared with themselves and with theoretical calculations based on the Bubbly Flow Model (reference [2]). All three sets of results compare well and lend further credance to the theoretical model. The best values of the two parameters in the model (K and M) are evaluated and recommended for use in applications.

The decision making process in flood mitigation typically involves a number of factors reflecting flood severity, flood vulnerability and the cost of the mitigation measures, which implies that the decision framework needs to combine both social-economic parameters and flood extent prediction analysis. A socio-economic vulnerability index (SEVI) is developed here to represent social-economic factors and its use demonstrated within a multi-criteria decision analysis (MCDA) for assessing flood levee options for a central basin of Jakarta, Indonesia. The variables defining the SEVI are selected based on available national social-economic data reported for Indonesia with overlapping information removed using Pearson's correlation analysis. Two different methods are used to further scale the SEVI which is developed along administrative boundaries into a Net SEVI which is dependent on the predicted flood hazard as resulting from the levee plan options while capturing uncertainty in the rainfall forecasting. The MCDA technique adopted uses criteria of Net SEVI, annual expected loss, graduality and levee construction cost for analyzing six different levee plans and with uncertainty in the rainfall incorporated. The Net SEVI thus specifically reflects the social-economic impact on the flood-affected population, and this approach thereby provides a higher degree of granularity in the flood mitigation decision process. The MCDA decision framework developed is general in that the Net SEVI can be applied for consideration of other flood mitigation strategies. Here, it is shown that the inclusion of the Net SEVI criteria changes the best choice levee plan decision to a higher protection level for the basin considered.

No abstract

The structure and mixing dynamics of shallow tropical reservoirs was investigated using data collected in the Kranji Reservoir in Singapore. Water temperature data spanning a 2 month period in 2007 shows that diurnal cycles of stratification and destratification were formed in various locations in the reservoir. Temperature stratification of 0.5°C to 3.5°C was formed during the daylight hours and reduced nightly when cooling occurred. Substantial horizontal redistribution of heat was also observed between the side arms and the main body of the reservoir. The Kranji's dynamics can be summarized in terms of three physical forcing regimes: a solar radiation—dominated regime, a windy regime, and a cold inflow regime. We delineate the three physical forcing regimes by two potentially useful dimensionless numbers that quantify the relative influences of surface heating, wind stirring, and inflow buoyancy fluxes. For most of the measurement period (88% of the data record), the solar radiation—dominated regime characterized the hydrodynamics. In spite of the dominance of solar radiation in setting local stratification, it is shown that Kranji Reservoir is a three‐dimensional system in which there can be significant variations in temperature in the vertical and along‐reservoir directions, as determined by cold inflow events, differential heating, and reservoir releases. Moreover, the data suggest that the dynamical balance of the Kranji system is sensitive to small forcing events, with the timescales of stratification and mixing as short as a day or less.