Laboratory studies of dissolved radiolabelled microcystin-LR in lake water

The fate of dissolved microcystin-LR was studied in laboratory experiments using surface water taken from a eutrophic lake. Based on initial range finding, a concentration of 50 microg l(-1) dissolved 14C-microcystin-LR was selected for subsequent time-course experiments. The first was performed in May before the cyanobacterial bloom season and low increases in the radioactivity of particulate fractions occurred with an approx. halving of the cyano-toxin during 4 days. The radioactivity of the dissolved fraction remained stable and there was no significant formation of radiolabelled inorganic carbon. A second time-course experiment was performed in September during the cyanobacterial bloom season. At the end of the four-day incubation period, the microcystin-LR concentration had decreased to an undetectable level and 24% of the added radiolabelled substance was found in different particulate fractions. The study demonstrated that biodegradation of dissolved microcystin-LR occurred in water collected at a lake surface with carbon dioxide as a major end-product.     

Effects of surface run-off on the transport of agricultural chemicals to ground water in a sandplain setting

An experiment was conducted at a depressional (lowland) and an upland site in sandy soils to evaluate the effects of surface run-off on the transport of agricultural chemicals to ground water. Approximately 16.5 cm of water was applied to both sites during the experiment, representing a natural precipitation event with a recurrence interval of approximately 100 years. Run-off was quantified at the lowland site and was not detected at the upland site during the experiment. Run-off of water to the lowland site was the most important factor affecting differences in the concentrations and fluxes of the agricultural chemicals between the two sites. Run-off of water to the lowland site ppears to have played a dual role by diluting chemical concentrations in the unsaturated zone as well as increasing the concentrations at the water table, compared to the upland site. Concentrations of chloride, nitrate and atrazine plus metabolites were noticeably greater at the water table than in the unsaturated zone at both sites. The estimated mass flux of chloride and nitrate to the water table during the test were 5-2 times greater, respectively, at the lowland site compared to the upland site, whereas the flux of sulfate and atrazine plus metabolites was slightly greater at the upland site. Results indicate that matrix flow of water and chemicals was the primary process causing the observed differences between the two sites. Results of the experiment illustrate the effects of heterogeneity and the complexity of evaluating chemical transport through the unsaturated zone.     

Computer-aided regional planning

The ISP computer system for interactive spatial planning was originally developed as a part of a project concerning land-use planning in the Malmö region of Sweden. In its first versions it was set up for use on mainframe computers. Land-use models were developed using this version of the computer system for Stockholm and Perth. During the last few years the system has been redesigned for a sun workstation environment. The background for this redevelopment has been the use of the system for the preparation of a land-use plan for the metropolitan region of Helsinki. The philosophy of the ISP system is to develop an interactive work environment for the generation and evaluation of land-use plan alternatives. The focus is on man-machine interaction and flexibility of model development. The current paper outlines the properties of the current version of the ISP system and the traits of the models designed for Perth and Helsinki planners. The paper uses the Perth application to demonstrate the modelling capabilities within the system. The Helsinki application is used as a means to illustrate some traits of the graphics interface.     

HF2V dissipator effects on the performance of a 3 story moment frame

In this paper, the seismic performance of the as-designed SAC Los Angeles 3 story seismic frame with rigid moment connections at the beam ends is compared with that of the same frame using semirigid connections with high force-to-volume (HF2V) lead dissipators. The presence of the gravity frames in the model is also considered. It was found that the placement of dissipators, ignoring the effect of the gravity frames, caused a 12% increase in period of the frame due to the decreased stiffness of the connections. During design level ground shaking the semi-rigid connections with HF2V dissipators have slightly lower accelerations, up to an 80% increase in peak drift, and a 200% increase in the permanent displacement compared to the as-designed case, but no structural damage is expected. When the gravity frames are considered, the floor accelerations decrease further, the peak displacements do not significantly change, but the residual story dirft ratios reduce to approximately 0.17%. This result is less than one half that of the as-designed frame, where typically gravity frame effects are not considered. The realistic analyses combining HF2V lead dissipators with gravity frames and well-designed non-structural elements creates a system with almost no structural damage and low residual displacements.     

An improved cryo-jet freezing method

A new cryo-jet freezing apparatus is described that is easy to use and gives good results using a propane-butene mixture (3: 1). Our use of the freezer in the study of mouse spinal cord explant cultures is discussed. At the tissue surface, the quality of tissue preservation from freezing, followed by freeze substitution, rivals that of conventional electron microscopic methods. Certain intracellular structures are better visualized using our methods. There is no evidence of the tissue being distorted by the cryogen jet when the freezer is operated correctly. A new freeze substitution device is also discussed.     

Synthesis and electronic spectra of some azo disperse dyes derived from N-2,2,2-trifluoroethyl-1,2,3,4-tetrahydroquinoline

Several monoazo dyes suitable for transfer printing have been prepared from N-2,2,2-trifluoroethyl-1,2,3,4-tetrahydroquinoline and compared with their N-ethyl counterparts. The presence of a trifluoroethyl group brings about considerable improvements in lightfastness properties on both polyester and nylon. Electron withdrawal by the trifluoroethyl substituent leads to hypsochromic shifts of the visible absorption band and also results in a marked positive halochromism.     

Neuronal diversity in the subiculum: correlations with the effects of somatostatin on intrinsic properties and on GABA-mediated IPSPs in vitro

1. We used intracellular current-clamp techniques to record from 33 ventral subicular neurons in slices or rat hippocampal formation. Presumed pyramidal neurons were characterized by their responses to depolarizing current pulses as either intrinsically burst firing (IB) or regular spiking (RS). Within the subiculum, IB cells were encountered most frequently in the deep cell layer, whereas RS cells were encountered most frequently in the superficial cell layer. IB cells had more depolarized resting potentials, lower input resistances, and more sag in their voltage responses to hyperpolarizing current pulses. 2. Somatostatin (5 microM) applied in the bathing medium caused a hyperpolarization and reduction in input resistance. These effects were of greater magnitude in IB cells. Somatostatin had no effect on sag in either cell type. These effects of somatostatin were unchanged in the presence of gamma-aminobutyric acid (GABA) receptor antagonists. 3. In a series of experiments conducted in RS cells only, somatostatin reduced the amplitude of the late but not the early component of evoked biphasic inhibitory postsynaptic potentials (IPSPs). 4. A second series of experiments was conducted in RS and IB cells. Somatostatin reduced the amplitude of pharmacologically isolated GABAA IPSPS in both cell types. In IB cells but not RS cells there was a correlation between this effect and the somatostatin-induced hyperpolarization. Somatostatin also reduced the amplitude of isolated GABAB IPSPS in both cell types, but more so in IB cells. 5. Somatostatin had no effect on the reversal potential of either IPSP in either cell type and no effect on the GABAA-mediated conductance in either cell type. In contrast, the GABAB-mediated conductance was reduced, especially in IB cells. 6. The effects of somatostatin on GABAA IPSPS are principally a result of membrane shunting and reductions in ionic driving force, but these mechanisms do not account for the reduction in GABAB IPSPS. 7. We suggest that the combined effects of somatostatin are likely to alter the balance between fast and slow inhibition and to do so more in IB cells than in RS cells.     

Reversal of innate aversions: Attempts to induce a preference for chili peppers in rats.

Although humans frequently develop preferences for innately unpalatable bitter or irritant substances, such preferences are extremely rare in animals. An attempt was made to understand the nature of this difference by 5 experiments with Charles River albino rats, using chili pepper as the unpalatable substance. In parallel with major aspects of the human experience with chili pepper, Ss were exposed to it as a flavoring in all their food for periods up to 11 mo from birth without significant preference enhancement. Gradual introduction of chili into the diet also had no effect, nor did poisoning and safety experiences designed to teach Ss that only chili-flavored foods were safe to eat. Seven pairings of chili-flavored diet with prompt recovery from thiamine deficiency did significantly attenuate the innate aversion and may have induced a chili preference in at least 1 case. Extensive experience with chili did not reliably make Ss much less sensitive to its oral effects. The only reliable way to eliminate chili aversion in rats is to destroy their chemical irritant sense, which was accomplished in 1 group. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)