Phase precession through acceleration of local theta rhythm: a biophysical model for the interaction between place cells and local inhibitory neurons

Phase precession is one of the most well known examples within the temporal coding hypothesis. Here we present a biophysical spiking model for phase precession in hippocampal CA1 which focuses on the interaction between place cells and local inhibitory interneurons. The model's functional block is composed of a place cell (PC) connected with a local inhibitory cell (IC) which is modulated by the population theta rhythm. Both cells receive excitatory inputs from the entorhinal cortex (EC). These inputs are both theta modulated and space modulated. The dynamics of the two neuron types are described by integrate-and-fire models with conductance synapses, and the EC inputs are described using non-homogeneous Poisson processes. Phase precession in our model is caused by increased drive to specific PC/IC pairs when the animal is in their place field. The excitation increases the IC's firing rate, and this modulates the PC's firing rate such that both cells precess relative to theta. Our model implies that phase coding in place cells may not be independent from rate coding. The absence of restrictive connectivity constraints in this model predicts the generation of phase precession in any network with similar architecture and subject to a clocking rhythm, independently of the involvement in spatial tasks.     

DESCRIPTION OF THE SENSORY CHARACTERISTICS OF SPANISH UNIFLORAL HONEYS BY FREE CHOICE PROFILING

Different Spanish unifloral honeys (eucalyptus, sunflower, rosemary, thyme, lavender, citrus, anise, quercus, and lemon blossom) and one multifloral honey were studied by Free-Choice Profiling (FCP) analysis. Generalized Procrustes Analysis (GPA) applied to the FCP data allowed discrimination between samples and provided information on the attributes responsible for the differences observed. The honeys had significantly different sensory characteristics. Textural attributes were the predominant factor in discriminating between samples, and appearance (color included) was also correlated with GPA dimensions to a lesser extent.     

Effects of grazing on patch structure in a semi‐arid two‐phase vegetation mosaic

Abstract. Question: What are the grazing effects in the spatial organization and the internal structure of high and low cover patches from a two‐phase vegetation mosaic? Location: Patagonian steppe, Argentina. Methods: We mapped vegetation under three different grazing conditions: ungrazed, lightly grazed and heavily grazed. We analysed the spatial patterns of the dominant life forms. Also, in each patch type, we determined density, species composition, richness, diversity, size structure and dead biomass of grasses under different grazing conditions. Results: The vegetation was spatially organized in a two‐phase mosaic. High cover patches resulted from the association of grasses and shrubs and low cover patches were represented by scattered tussock grasses on bare ground. This spatial organization was not affected by grazing, but heavy grazing changed the grass species involved in high cover patches and reduced the density and cover of grasses in both patch types. Species richness and diversity in high cover patches decreased under grazing conditions, whereas in low cover patches it remained unchanged. Also, the decrease of palatable grasses was steeper in high cover patches than in low cover patches under grazing conditions. Conclusions: We suggest that although grazing promotes or inhibits particular species, it does not modify the mosaic structure of Patagonian steppe. The fact that the mosaic remained unchanged after 100 years of grazing suggests that grazing does not compromize population processes involved in maintaining patch structure, including seed dispersal, establishment or biotic interactions among life forms.     

Relations Between River Plant Richness in the Portuguese Floodplains and the Widespread Water Knotgrass <Emphasis Type="Italic">(Paspalum Paspalodes</Emphasis>)

We examined the variability of macroinvertebrate assemblage structure, species identities, and functional feeding group composition in relation to stream size, tributary position, and in-stream factors in a boreal watershed in Finland. Our study included three riffle sites in each of three stream sections in each of three stream size classes. Multi-response permutation procedure, indicator value method, and canonical correspondence analysis revealed clear differences in assemblage structure among the stream size classes, with a gradual increase of species richness as the stream size increased. Significant differences in assemblage structure were also found among the tributary river systems. The functional feeding group composition broadly followed the river continuum concept, i.e., headwaters were dominated by shredders, gatherers, or filterers, whereas scrapers increased in relative abundance with stream size. There was, however, considerable variation in the functional feeding group composition both among and within the headwater stream sections. Our findings refer to a strong influence of stream size on macroinvertebrate assemblages, but also factors prevailing at the scale of individual riffles should be considered in biodiversity conservation of lotic ecosystems.     

Impacts of inter-basin water transfer on the water quality of receiving reservoirs in a tropical semi-arid region

Inter-basin water transfer (IBWT) involves the transport of water from one geographically distinct basin to another to balance the distribution of water resources. Although the socio-economic benefits of implementing these projects are well recognized, little is known about the subsequent effects on the water quality of the receiving systems. We evaluated the effects of an IBWT on the water quality of three receiving reservoirs of an intermittent river in a semi-arid region. We compared the similarity among the reservoirs before and after the IBWT to assess how the reservoirs responded to the introduction of water. Although the last two reservoirs that have received water have become similar in terms of physical and chemical characteristics and algal biomass (chlorophyll-a), the first reservoir has not. The IBWT resulted in an improvement in the water quality of the first reservoir but a decrease in the water quality of the two successive reservoirs, along with a significant increase in algal biomass. Long river sections located upstream that were dry at the time of IBWT probably contributed nutrients to the water as it moved downstream and into the reservoirs. Significant differences in the water quality were observed for different sampling months after the IBWT, but not for different sampling depths. Before the IBWT, the predictor variables for algal biomass were basically transparency and non-algal turbidity, with which it established a positive relationship. After IBWT, however, algal biomass also showed a positive relationship with pH and temperature. We conclude that IBWT affects the water quality of receiving reservoirs and that the responses are reservoir specific. IBWT also increases the complexity of the correlations of physical and chemical variables with algal biomass.

     

Microbial population dynamics on Golden Delicious apples from bud to harvest and effect of fungicide applications

The microbial population dynamics on apples cv. Golden Delicious were analysed every 15 days between bud and harvest in a fully replicated experiment in northern Spain in 1994 and 1995. The total microbial populations varied with developmental stage, and with prevailing climatic conditions. The predominant mycroflora were the filamentous fungi Cladosporium and Alternaria spp. and white and pink yeasts. Other genera isolated included mainly species of Epicoccum, Fusarium and Acremonium. However, the most important post-harvest pathogens Penicillium expansum and Botrytis cinerea were seldom isolated from ripening apples. Maximum total filamentous fungal populations occurred after fruit set and during early ripening [2 × 10⁴cfu (colony-forming units) g^-1 approximately] while those of bacteria were maximum at bud stage (3.5 × 10⁵and 3.0 × 10⁴ cfu g^-1 in 1994 and 1995 respectively). White yeasts were more numerous than pink yeasts. Endophytic infection of apple buds by Alternaria spp., responsible for core rot, was found in almost all bud tissue. By contrast, Cladosporium spp. were initially isolated later from 12.5–50% of tissue samples during blooming and fruit set. The impact of a four-spray fungicide regime during apple development significantly decreased the total filamentous fungal populations in both years, and that of Cladosporium spp. in 1994. However, bacterial populations were often higher on apples from fungicide-treated plots. Fungicide sprays decreased populations of Cladosporium, Alternaria and white yeasts for a maximum of up to 15–30 days after application. Fungicide application had little effect on endophytic infection of apples by Alternaria spp. between bud and harvest.     

Synthesis of 2-ethylhexyl oleate catalyzed by Candida antarctica lipase immobilized on a magnetic polymer support in continuous flow

Bioprocess and Biosystems Engineering - This study investigated the synthesis of 2-ethylhexyl oleate catalyzed by Candida antarctica lipase immobilized on magnetic poly(styrene-co-divinylbenzene)...     

TASTE GROUP THRESHOLDS AND SENSORY EVALUATION OF SPANISH WINE VINEGARS

Wine vinegar is a product obtained from wine acidification which contains at least 5% by wt. of acetic acid, in general without any additives or colorings.
Aspects studied in this work include: the determination of the taste group thresholds (geometric mean of the individual best-estimate thresholds "BET") of two different acids (citric and acetic acids) in aqueous solution and spanish vinegars produced from table and sherry wines. The results obtained suggest that wine vinegar can be considered something more than just an acidulant agent.
In order to evaluate differences among wine vinegars, discriminant tests for twenty-five spanish vinegars (sherry, table and flavored vinegars) were applied. Six of the twelve attributes freely chosen by assessors allowed grouping of the spanish wine vinegars according to their sensory aspects.