Hysteretic optimization for the Sherrington-Kirkpatrick spin glass

Hysteretic optimization is a heuristic optimization method based on the observation that magnetic samples are driven into a low energy state when demagnetized by an oscillating magnetic field of decreasing amplitude. We show that hysteretic optimization is very good for finding ground states of Sherrington-Kirkpatrick spin glass systems. With this method it is possible to get good statistics for ground state energies for large samples of systems consisting of up to about 2000 spins. The way we estimate error rates may be useful for some other optimization methods as well. Our results show that both the average and the width of the ground state energy distribution converges faster with increasing size than expected from earlier studies.Comment: Physica A, accepte

Institutional investors and stock market efficiency: The case of the January anomaly

In this paper, we investigate the effect of institutional investors on the January stock market anomaly. The Polish and Hungarian pension system reforms and the associated increase in investment activities of pension funds are used as a unique institutional characteristic to provide evidence on the impact of individual versus institutional investors on the January effect. We find robust empirical results that the increase in institutional ownership has reduced the magnitude of an anomalous January effect induced by individual investors’ trading behavior.Institutional traders; Individual investors; January effect; Polish and Hungarian pension fund investors

Integration of Horizontally Transferred Genes into Regulatory Interaction Networks Takes Many Million Years

Adaptation of bacteria to new or changing environments is often associated with the uptake of foreign genes through horizontal gene transfer. However, it has remained unclear how (and how fast) new genes are integrated into their host's cellular networks. Combining the regulatory and protein interaction networks of Escherichia coli with comparative genomics tools, we provide the first systematic analysis of this issue. Genes transferred recently have fewer interaction partners compared to nontransferred genes in both regulatory and protein interaction networks. Thus, horizontally transferred genes involved in complex regulatory and protein-protein interactions are rarely favored by selection. Only few protein-protein interactions are gained after the initial integration of genes following the transfer event. In contrast, transferred genes are gradually integrated into the regulatory network of their host over evolutionary time. During adaptation to the host cellular environment, horizontally transferred genes recruit existing transcription factors of the host, reflected in the fast evolutionary rates of the cis-regulatory regions of transferred genes. Further, genes resulting from increasingly ancient transfer events show increasing numbers of transcriptional regulators as well as improved coregulation with interacting proteins. Fine-tuned integration of horizontally transferred genes into the regulatory network spans more than 8-22 million years and encompasses accelerated evolution of regulatory regions, stabilization of protein-protein interactions, and changes in codon usage

The influence of propolis application to meat utility on ROSS 308 broiler chickens

The aim of the experiment was to monitor the impact of propolis extract (experimental group) for meat utility of the Ross 308 chicken. The dosage of propolis was 0.2 g.kg KKZ-1 throught the fattening (40 days). Application of propolis increased (P≤0.01) slaughter weight (+76.80 g) and carcass weight (+67.90 g) in hens compared to the control group (1790.60 g, resp. 1266.54 g). In group with roosters slaughter weight (+70.80 g) and carcass weight (+56.00 g) were also increased (P≥0.05) in the experimental group compared to control (2086.20 g, resp. 1475.20 g). Offal weight in both sexes was lower (P≥0.05) in the experimental group (135.55 g - ♀, 158.21 g - ♂) compared to control (140.75 g - ♀, 168.55 g - ♂). Carcass yield was higher in hens (P≥0.05) in the experimental group (78.71 %) versus control (78.60 %).The evaluation of meat utility Ross 308 chickens  without distinction of sex did not show significant differences (P≥0.05), but a slight increase in slaughter weight and in the carcass weight in group with application of propolis extract in their fattening. Contrary slightly lower offal weight (-7.77 g) and carcass yield (-0.21 %) were found in the experimental group of chickens without distinction of sex (P≥0.05) compared to control group (weight of offal - 154.65 g, carcass yield - 78.69 %). We recommend the application of propolis as a possible supplement in the fattening of chickens, as it increases the performance parameters of meat and may also positively affect the economy of production

Temporal disparity of action potentials triggered in axon initial segments and distal axons in the neocortex

Neural population activity determines the timing of synaptic inputs, which arrive to dendrites, cell bodies, and axon initial segments (AISs) of cortical neurons. Action potential initiation in the AIS (AIS-APs) is driven by input integration, and the phase preference of AIS-APs during network oscillations is characteristic to cell classes. Distal regions of cortical axons do not receive synaptic inputs, yet experimental induction protocols can trigger retroaxonal action potentials (RA-APs) in axons distal from the soma. We report spontaneously occurring RA-APs in human and rodent cortical interneurons that appear uncorrelated to inputs and population activity. Network-linked triggering of AIS-APs versus input-independent timing of RA-APs of the same interneurons results in disparate temporal contribution of a single cell to in vivo network operation through perisomatic and distal axonal firing

Institutional investors and stock market efficiency: The case of the January anomaly

In this paper, we investigate the effect of institutional investors on the January stock market anomaly. The Polish and Hungarian pension system reforms and the associated increase in investment activities of pension funds are used as a unique institutional characteristic to provide evidence on the impact of individual versus institutional investors on the January effect. We find robust empirical results that the increase in institutional ownership has reduced the magnitude of an anomalous January effect induced by individual investors’ trading behavior