Amplitude and phase relationship between alpha and beta oscillations in the human electroencephalogram.

The relationship between the electro-encephalographic (EEG) alpha and beta oscillations in the resting condition was investigated in the study. EEGs were recorded in 33 subjects, and alpha (7.5-12.5 Hz) and beta (15-25 Hz) oscillations were extracted with the use of a modified wavelet transform. Power, peak frequency and phase synchronisation were evaluated for both types of oscillation. The average beta-alpha peak frequency ratio was about 1.9-2.0 for all electrode derivations. The peak frequency of beta activity was within 70-90 % of the 95 % confidence interval of twice the alpha frequency. A significant (p < 0.05) linear regression was found between beta and alpha power in all derivations in 32 subjects, with the slope of the regression line being approximately 0.3. There was no significant difference in the slope of the line in different electrode locations, although the power correlation was strongest in the occipital locations where alpha and beta oscillations had the largest power. A significant 1:2 phase synchronisation was present between the alpha and beta oscillations, with a phase lag of about pi/2 in all electrode derivations. The strong frequency relationship between the resting beta and alpha oscillations suggests that they are generated by a common mechanism. Power and phase relationships were weaker, suggesting that these properties can be modulated by additional mechanisms as well as be influenced by noise. A careful distinction between alpha-dependent and alpha-independent beta activity should be considered when making statements about the possible significance of genuine beta activity in different neurophysiological mechanisms.

Lactate dehydrogenase from the northern krill Meganyctiphanes norvegica: comparison with LDH from the Antarctic krill Euphausia superba.

Electrophoretic polymorphism of lactate dehydrogenase (LDH, EC 1.1.1.27) from abdominal muscle is reported in the northern krill Meganyctiphanes norvegica. In the population, from the Gullmarsfjord (west coast of Sweden), LDH was encoded for by two different Ldh-A* and -B* loci. The isoenzymes were named according to their electrophoretic mobilities. Ldh-A* locus was polymorphic. The allelic frequencies were a=0.99, a'=0.002, a"=0.004, a"'=0.004. The level of LDH polymorphism is low. Most individuals possess the same amount of two LDH homopolymers (LDH-A*(4) and LDH-B*(4)). The Meganyctiphanes norvegica LDH-A*(4) and LDH-B*(4) isoenzymes and the predominant LDH-A*(4) isoenzyme from Euphausia superba were purified to specific activities of 294, 306 and 464 micromol NADH min(-1) mg(-1), respectively. In both species the LDH isoenzymes were separated by chromatofocusing. All three isoenzymes are L-specific tetramers with molecular weight of approximately 160 kDa. Northern krill LDH-A*(4) has higher affinity for pyruvate and lactate and is more thermostable than LDH-B*(4). Both isoenzymes are inhibited significantly by high concentration of pyruvate but not lactate. Antarctic krill isoenzyme exhibits high substrate affinities, high NAD inhibition, high inhibition at 10 mM pyruvate, lack of lactate inhibition, and high heat stability and resembles northern krill LDH-A*(4) isoenzyme.

Low bit-rate efficient compression for seismic data.

Compression is a relatively new introduced technique for seismic data operations. The main drive behind the use of data compression in seismic data is the very large size of seismic data acquired. Some of the most recent acquired marine seismic data sets exceed 10 Tbytes, and in fact there are currently seismic surveys planned with a volume of around 120 Tbytes. Thus, the need to compress these very large seismic data files is imperative. Nevertheless, seismic data are quite different from the typical images used in image processing and multimedia applications. Some of their major differences are the data dynamic range exceeding 100 dB in theory, very often it is data with extensive oscillatory nature, the x and y directions represent different physical meaning, and there is significant amount of coherent noise which is often present in seismic data. Up to now some of the algorithms used for seismic data compression were based on some form of wavelet or local cosine transform, while using a uniform or quasiuniform quantization scheme and they finally employ a Huffman coding scheme. Using this family of compression algorithms we achieve compression results which are acceptable to geophysicists, only at low to moderate compression ratios. For higher compression ratios or higher decibel quality, significant compression artifacts are introduced in the reconstructed images, even with high-dimensional transforms. The objective of this paper is to achieve higher compression ratio, than achieved with the wavelet/uniform quantization/Huffman coding family of compression schemes, with a comparable level of residual noise. The goal is to achieve above 40 dB in the decompressed seismic data sets. Several established compression algorithms are reviewed, and some new compression algorithms are introduced. All of these compression techniques are applied to a good representation of seismic data sets, and their results are documented in this paper. One of the conclusions is that adaptive multiscale local cosine transform with different windows sizes performs well on all the seismic data sets and outperforms the other methods from the SNR point of view. All the described methods cover wide range of different data sets. Each data set will have his own best performed method chosen from this collection. The results were performed on four different seismic data sets. Special emphasis was given to achieve faster processing speed which is another critical issue that is examined in the paper. Some of these algorithms are also suitable for multimedia type compression.

Fast adaptive wavelet packet image compression.

Wavelets are ill-suited to represent oscillatory patterns: rapid variations of intensity can only be described by the small scale wavelet coefficients, which are often quantized to zero, even at high bit rates. Our goal is to provide a fast numerical implementation of the best wavelet packet algorithm in order to demonstrate that an advantage can be gained by constructing a basis adapted to a target image. Emphasis is placed on developing algorithms that are computationally efficient. We developed a new fast two-dimensional (2-D) convolution decimation algorithm with factorized nonseparable 2-D filters. The algorithm is four times faster than a standard convolution-decimation. An extensive evaluation of the algorithm was performed on a large class of textured images. Because of its ability to reproduce textures so well, the wavelet packet coder significantly out performs one of the best wavelet coder on images such as Barbara and fingerprints, both visually and in term of PSNR.

Adaptive regularized constrained least squares image restoration.

In noisy environments, a constrained least-squares (CLS) approach is presented to restore images blurred by a Gaussian impulse response, where instead of choosing a global regularization parameter, each point in the signal has its own associated regularization parameter. These parameters are found by constraining the weighted standard deviation of the wavelet transform coefficients on the finest scale of the inverse signal by a function r which is a local measure of the intensity variations around each point of the blurred and noisy observed signal. Border ringing in the inverse solution is proposed decreased by manipulating its wavelet transform coefficients on the finest scales close to the borders. If the noise in the inverse solution is significant, wavelet transform techniques are also applied to denoise the solution. Examples are given for images, and the results are shown to outperform the optimum constrained least-squares solution using a global regularization parameter, both visually and in the mean squared error sense.

Exponential growth, random transitions and progress through the G1 phase: computer simulation of experimental data.

At a time of increasing knowledge of gene and molecular regulation of cell cycle progression, a re-evaluation is presented concerning a phenomenon discussed before the present expanding era of cell cycle research. 'Random transition' and exponential slopes of alpha- and beta-curves were conceived in the 1970s and early 1980s to explain cell cycle progression. An exponential behaviour of the beta-curve was claimed as being necessary and sufficient for a 'random transition' in the cell cycle. In our present work, similar slopes of those curves were shown to materialize when the increase in mass of single cells was set as exponential in a structured cell cycle model where DNA replication and increase in cell mass were postulated to be two loosely coupled subcycles of the cell cycle, without introducing any 'random transition'. Findings published in the 1980s demonstrating the effect of serum depletion of 3T3 Balb-c cells were simulated and the shallower slope of the alpha- and beta-curves found experimentally could be attributed to the reduced rate of exponential growth in cell mass, rather than to a reduced 'transition probability'.

Cell cycle progression: computer simulation of uncoupled subcycles of DNA replication and cell growth.

A computer simulation is presented for cell proliferation in a structured cell cycle model. The simulation takes into account the idea that DNA replication and cell growth are two loosely coupled subcycles. The simulation experiments performed offer an explanation for the close correlation often found in interdivision times of sister cell pairs and demonstrate that the exponential slope of the so-called beta-curve is linked to an exponential increase in cell mass. However, in synchronization experiments, a linear increase in mean mass of a cell population develops over time. A channel is opened for a genetic and growth rate influence extending from grandparent to granddaughter. Positive and negative time correlations close to zero still occurred for mother-daughter cell cycles. The computer program leaves two sites in the cell cycle available for gene, molecular and size checkpoints, one in G1 and one in G2. The simulation experiments bridge the gap between models considering (i) size control, (ii) transition probability, and (iii) inherited properties as interpretations of cell cycle progression and are applicable to embryonic cells with the potential to differentiate, somatic cells, and to the kinetics of activation of serum-starved cells. A G0 state is also defined.

Infestation dynamics of external parasites of saithe (Pollachius virens) from the North and Norwegian Seas.

An attempt has been made to examine the saithe's external parasites with respect to host age and the reproduction time of Clavella adunca in the North Sea. 1835 specimens of Pollachius virens caught in 1976-1980 and 1986 were examined. They were infested with Diclidophora denticulata, Udonella caligorum (Monogenea) and Clavella adunca, Lepeophtheirus pollachius, Caligus elongatus (Copepoda). The large number of adult females of C. adunca in winter and spring, the juvenile forms in summer and forms of 4th developmental phase autumn suggest that the reproduction cycle runs over the year in the North Sea with the peak between the late spring and early summer. The intensity values of infestation are highest for sexually mature fish but fall in older ones.

Evidence for an intraclonal random shift between two types of cell cycle times in an embryonal carcinoma cell line.

In a recent paper we reported the discovery of an intraclonal bimodal-like cell cycle time variation within the multipotent embryonal carcinoma (EC) PCC3 N/1 line growing in the exponential phase in the undifferentiated state. The variability was found to be localized in the G1 period. Furthermore, an inverse relation between cell size and cell generation time was found in the cell system analysed. It was suggested that the bimodal-like intraclonal time variability previously reported was attributable to an intraclonal shift between two types of cell-growth-rate cycles and that the cell-growth cycle has a supramitotic character, being dissociated from the DNA-division cycle. The growth rate heterogeneity in the cell population was found to need three cell cycles to reach full dispersion in time. This was assumed to be due to a decreased inheritance from sister cell pairs to second cousin cell pairs. Thus, the interesting feature is that in one and the same multipotent cell line there was evidence for an intraclonal instability with a random shift between two types of cell cycle differing in the duration of their G1 period.

Growth rate regulation and random transition. A study performed on embryonal carcinoma cell lines. I.

Analyses of cell-cycle characteristics of the three embryonal carcinoma (EC) cell lines F9, PCC3 N/1 and PCC4 Azal, have been performed. The three lines reflect successive stages in early mouse embryogenesis as regards cell surface antigens and cell-cycle characteristics. In an attempt to understand changes in cell-cycle characteristics occurring during early embryogenesis, the two-random transition probability (TP) model was applied to the EC-cell system--and particularly to the F9 line. By utilizing an intraclonal heterogeneity in intermitotic times found in these EC lines, a growth-regulating point was introduced as a modification of the two-random TP model. The modified model was found to be very useful when demonstrating the cell-cycle growth kinetics of the F9 line. The model is used in an accompanying paper to extend the analysis of cell-cycle characteristics in undifferentiated EC cells.

Cell growth and cell division: dissociated and random initiated? A study performed on embryonal carcinoma cell lines. II.

The 'random transition probability' cell-cycle models have so far failed to convincingly link the transition events with phenomena describable by biochemical methods. The study presented was carried out on the F9 and PCC3 N/1 embryonal carcinoma (EC) cell lines. We now report an extended analysis of the two-random transition probability (TP) model and preliminary results are presented showing that the deterministic L period in that model can be regarded as reflecting the 'cell-growth cycle'. Evidence is presented that suggests that the 'cell-growth cycle' is a supramitotic deterministic phase--i.e. starting in one cell cycle and being completed in the next following G1 period and dissociated from the 'DNA-division cycle'. This phenomenon makes an interesting contribution to the old knowledge of a stepwise G1 prolongation during early embryogenesis in yielding a mechanism by which the cell can alter the ratio of nucleus to cytoplasm prior to the onset of gene expression.

A comparative study of the cell cycles of nullipotent and multipotent embryonal carcinoma cell lines during exponential growth.

Three embryonal carcinoma (EC) cell lines F9, PCC4 Azal, and PCC3 N/1 with a common origin from the transplantable ascites teratoma OTT6050 were analyzed with regard to cell cycle characteristics during exponential growth in the undifferentiated state. The three lines, in the sequence mentioned, have been shown to represent successive stages in early normal mouse embryogenesis from morula to blastocyst, as reflected in their cell surface antigens. In the multipotent lines an increased intraclonal variability in intermitotic times was found when analyzing family trees. In the PCC3 N/1 line the distribution was almost bimodal. The increased intermitotic time variability was found to be represented in the G1 period that varied from less than 1 hr up to about 6 hr in the PCC3 N/1 line, with a mean value of 3.4 hr. The G1 period of the F9 line had a range of only 3.5 hr, with a mean value of 1.5 hr. The S-G2 period was found to be very similar in length in all three lines.