Subsampling effects in neuronal avalanche distributions recorded in vivo

Background  

Many systems in nature are characterized by complex behaviour where large cascades of events, or avalanches, unpredictably alternate with periods of little activity. Snow avalanches are an example. Often the size distribution f(s) of a system's avalanches follows a power law, and the branching parameter sigma, the average number of events triggered by a single preceding event, is unity. A power law for f(s), and sigma = 1, are hallmark features of self-organized critical (SOC) systems, and both have been found for neuronal activity in vitro. Therefore, and since SOC systems and neuronal activity both show large variability, long-term stability and memory capabilities, SOC has been proposed to govern neuronal dynamics in vivo. Testing this hypothesis is difficult because neuronal activity is spatially or temporally subsampled, while theories of SOC systems assume full sampling. To close this gap, we investigated how subsampling affects f(s) and sigma by imposing subsampling on three different SOC models. We then compared f(s) and sigma of the subsampled models with those of multielectrode local field potential (LFP) activity recorded in three macaque monkeys performing a short term memory task.     

Physicochemical characterization of the endotoxins from Coxiella burnetii strain Priscilla in relation to their bioactivities

Background  

Coxiella burnetiiis the etiological agent of Q fever found worldwide. The microorganism has like other Gram-negative bacteria a lipopolysaccharide (LPS, endotoxin) in its outer membrane, which is important for the pathogenicity of the bacteria. In order to understand the biological activity of LPS, a detailed physico-chemical analysis of LPS is of utmost importace.     

Infrared spectral comparison of 5-aminolevulinic acid and its hexyl ester

5-aminolevulinic acid (ALA) and its hexyl ester (ALA-H) are bioorganic molecules, now used as drugs in the study and clinical application of photodynamic therapy (PDT). Their infrared spectra were reported in first time here. The spectral characteristic was found well correlated to their structure feature. The strong peaks of C=O, C-H(2) and O-H band were shown in ALA spectrum. While in case of ALA-H, besides the vibration modes of C=O and CH(2) the additional CH(3) infrared peaks appeared, which correspond with their structural difference. Thus the infrared spectrum could be used to detect and distinguish ALA and ALA-H, which have potential for the mechanism study of ALA and ALA-H based PDT in biological system. Using the infrared spectrum as the probe, the thermal effect on structure stability was detected. Below the temperature of 80 degrees C, the ALA and ALA-H are thermally stable in structure. When temperature reached 120 degrees C, the serious structure breaking (thermal decomposition) happened for both ALA and ALA-H.