Spectral analysis of coniferous foliage and possible links to soil chemistry: are spectral chlorophyll indices related to forest floor dissolved organic C and N?

Dissolved organic matter in soils can be predicted from forest floor C:N ratio, which in turn is related to foliar chemistry. Little is known about the linkages between foliar constituents such as chlorophylls, lignin, and cellulose and the concentrations of water-extractable forest floor dissolved organic carbon and dissolved organic nitrogen. Lignin and cellulose are not mobile in foliage and thus may be indicative of growing conditions during prior years, while chlorophylls respond more rapidly to the current physiological status of a tree and reflect nutrient availability. The aim of this study was to examine potential links among spectral foliar data, and the organic C and N of forest soils. Two coniferous species (red spruce and balsam fir) were studied in the White Mountains of New Hampshire, USA. Six trees of each species were sampled at 5 watersheds (2 in the Hubbard Brook Experimental Forest, 3 in the Bartlett Experimental Forest). We hypothesized that in a coniferous forest, chemistry of old foliage would better predict the chemical composition of the forest floor litter layer than younger foliage, which is the more physiologically active and the most likely to be captured by remote sensing of the canopy. Contrary to our expectations, chlorophyll concentration of young needles proved to be most tightly linked to soil properties, in particular water-extractable dissolved organic carbon. Spectral indices related to the chlorophyll content of needles could be used to predict variation in forest floor dissolved organic carbon and dissolved organic nitrogen. Strong correlations were found between optical spectral indices based on chlorophyll absorption and forest floor dissolved organic carbon, with higher foliage chlorophyll content corresponding to lower forest floor dissolved organic carbon. The mechanisms behind these correlations are uncertain and need further investigation. However, the direction of the linkage from soil to tree via nutrient availability is hypothesized based on negative correlations found between foliar N and forest floor dissolved organic carbon.     

Parameters of spike trains observed in a short time window

We study the estimation of statistical moments of interspike intervals based on observation of spike counts in many independent short time windows. This scenario corresponds to the situation in which a target neuron occurs. It receives information from many neurons and has to respond within a short time interval. The precision of the estimation procedures is examined. As the model for neuronal activity, two examples of stationary point processes are considered: renewal process and doubly stochastic Poisson process. Both moment and maximum likelihood estimators are investigated. Not only the mean but also the coefficient of variation is estimated. In accordance with our expectations, numerical studies confirm that the estimation of mean interspike interval is more reliable than the estimation of coefficient of variation. The error of estimation increases with increasing mean interspike interval, which is equivalent to decreasing the size of window (less events are observed in a window) and with decreasing the number of neurons (lower number of windows).     

DNA-inspired information concealing: A survey

Various research efforts would benefit from the ability to exchange and share information (traces with packet payloads, or other detailed system logs) to enable more data-driven research. Protection of the sensitive content is crucial for extensive information sharing. We present results of Kencl and Loebl (2009) [41] and Blamey et al. (in preparation) [4] about a technique of information concealing, based on introduction and maintenance of families of repeats. The structure of repeats in DNA constitutes an important obstacle for its reconstruction by hybridisation. A large proportion of eukaryotic genomes is composed of DNA segments that are repeated either precisely or in variant form more than once. As yet, no function has been associated with many of the repeats. In the paper by Blamey et al. (in preparation) [4], the authors propose that in eukaryotes the cells have DNA as a depositary of concealed genetic information and the genome achieves the self-concealing by accumulation and maintenance of repeats. The protected information may be shared and this is useful for the development of intercellular communication and in the development of multicellular organisms. The results presented here are protected by Czech patent number 301799 and by US Patent Application number 12/670.     

RF Bulk Acoustic Wave Resonators and Filters

Small sized, highly selective solidly mounted bulk acoustic wave (BAW) band pass filters are of great interest for mobile and wireless systems operating in the frequency range of 0.8 GHz up to more than 10 GHz. They can be fabricated on silicon or glass wafers using standard semiconductor integration techniques. These filters are based on electro-acoustic high Q resonators, which exploit the thickness extensional mode of a thin piezoelectric AlN or ZnO film. This film has to be grown with its polar axis, oriented perpendicular to the substrate. Both the deposition process and using a textured electrode support excellent c-axis oriented growth and thus high electromechanical coupling coefficient k _t and filter bandwidth. Modelling of the filter and resonator response is performed by means of a combination of a 1D electro-acoustic model together with an electromagnetic model. The paper shows examples of filters operating in the range between 2 and 8 GHz.     

Improved method for quantifying levoglucosan and related monosaccharide anhydrides in atmospheric aerosols and application to samples from urban and tropical locations

An improved analytical method was developed and validated for the determination of the monosaccharide anhydrides levoglucosan, mannosan, and galactosan in atmospheric aerosol samples. The method uses an external recovery standard, extraction in dichloromethane, trimethylsilylation, addition of an internal standard (1-phenyl dodecane), and analysis by gas chromatography with flame ionization detection (GC-FID) and gas chromatography/mass spectrometry (GC/MS). As external recovery standard, we selected 1,2,3-trihydroxyhexane, which has a similar polarity as the monosaccharide anhydrides; furthermore, it was ensured that the trimethylsilylation step leads to complete derivatization into trimethylsilyl ethers. The reproducibility of the combined trimethylsilylation and analysis of levoglucosan was about 2% for standard solutions, whereas the precision of the entire method for the sum of all three monosaccharide anhydrides (MAs) in real aerosol filter samples was about 5%. The method was applied to aerosol samples from urban and tropical locations. The atmospheric concentration of the MAs in fine (<2.5 microm) aerosols at a primary forest site in Rond?nia, Brazil, was on average 2.15 microg m(-3) during the dry season when intensive biomass burning occurs, which was almost 400 times higher than during the wet (nonburning) season. Urban total aerosols collected in Gent, Belgium, showed an average atmospheric concentration of MAs of 0.56 microg m(-3) for the winter season, which was a factor of 20 higher than for the summer season. The carbon in the MAs accounted on average for about 5.1% and 1.8% of the organic carbon in the Brazilian dry season and Gent winter aerosols, respectively. Levoglucosan was the major MA, with a relative abundance in the range of 76-93%.     

Study of Linkage between Glutathione Pathway and the Antibiotic Resistance of Escherichia coli from Patients’ Swabs

In this work, we focused on the differences between bacterial cultures of E. coli obtained from swabs of infectious wounds of patients compared to laboratory E. coli. In addition, blocking of the protein responsible for the synthesis of glutathione (γ-glutamylcysteine synthase—GCL) using 10 mM buthionine sulfoximine was investigated. Each E. coli showed significant differences in resistance to antibiotics. According to the determined resistance, E. coli were divided into experimental groups based on a statistical evaluation of their properties as more resistant and more sensitive. These groups were also used for finding the differences in a dependence of the glutathione pathway on resistance to antibiotics. More sensitive E. coli showed the same kinetics of glutathione synthesis while blocking GCL (K_m 0.1 µM), as compared to non-blocking. In addition, the most frequent mutations in genes of glutathione synthetase, glutathione peroxidase and glutathione reductase were observed in this group compared to laboratory E.coli. The group of “more resistant” E. coli exhibited differences in K_m between 0.3 and 0.8 µM. The number of mutations compared to the laboratory E. coli was substantially lower compared to the other group.