Collective decision making in cohesive flocks

Most of us must have been fascinated by the eye catching displays of collectively moving animals. Schools of fish can move in a rather orderly fashion and then change direction amazingly abruptly. There are a huge number of further examples both from the living and the non-living world for phenomena during which the many interacting, permanently moving units seem to arrive at a common behavioural pattern taking place in a short time. As a paradigm of this type of phenomena we consider the problem of how birds arrive at a decision resulting in their synchronized landing. We introduce a simple model to interpret this process. Collective motion prior to landing is modelled using a simple self-propelled particle (SPP) system with a new kind of boundary condition, while the tendency and the sudden propagation of the intention of landing is introduced through rules analogous to the random field Ising model in an external field. We show that our approach is capable of capturing the most relevant features of collective decision making in a system of units with a variance of individual intentions and being under an increasing level of pressure to switch states. We find that as a function of the few parameters of our model the collective switching from the flying to the landing state is indeed much sharper than the distribution of the individual landing intentions. The transition is accompanied by a number of interesting features discussed in this report

Effects of the disk tillage on soil condition, crop yield and weed infestation

This research was instigated by the fact that during the last decade annually repeated shallow disk tillage on the same field became frequent practice in Hungary. In order to study the changes of soil condition associated with disk tillage and to assess it is consequences, long-term tillage field experiments with different levels of nutrients were set up in 1991 (A) and in 1994 (B) on Chromic Luvisol at Gödöllö. The effects of disk tillage (D) and disk tillage combined with loosening (LD) on soil condition, on yield of maize and winter wheat, and on weed infestation were examined. The evaluation of soil condition measured by cone index and bulk density indicated that use of disking annually resulted in a dense soil layer below the disking depth (diskpan-compaction). It was found, that soil condition deteriorated by diskpan-compaction decreased the yield of maize significantly by 20 and 42% (w/w), and that of wheat by 13 and 15% (w/w) when compared to soils with no diskpan-compaction. Averaged over seven years, and three fertilizer levels, the cover % of the total, grass and perennial weeds on loosened soils were 73, 69 and 65% of soils contained diskpan-compaction

Bartonella infections in fleas (Siphonaptera : Pulicidae) and lack of Bartonellae in ticks (Acari : Ixodidae) from Hungary

Fleas (95 Pulex irritans, 50 Ctenocephalides felis, 45 Ctenocephalides canis) and ixodid ticks (223 Ixodes ricinus, 231 Dermacentor reticulatus, 204 Haemaphysalis concinna) were collected in Hungary and tested, in assays based on PCR, for Bartonella infection. Low percentages of P. irritans (4.2%) and C. felis (4.0%) were found to be infected. The groEL sequences of the four isolates from P. irritans were different from all the homologous sequences for bartonellae previously stored in GenBank but closest to those of Bartonella sp. SE-Bart-B (sharing 96% identities). The groEL sequences of the two isolates from C. felis were identical with those of the causative agents of cat scratch disease, Bartonella henselae and Bartonella clarridgeiae, respectively. The pap31 sequences of B. henselae amplified from Hungarian fleas were identical with that of Marseille strain. No Bartonella-specific amplification products were detected in C. canis, L ricinus, D. reticulatus and H. concinna pools

Floor Slabs Which are Frightening From Underneath, But Following Minor Repair Repeatedly Durable

The paper is intended to deal with a certain failure of a floor slab type, which was favored in the beginning of the 20th century in Hungary. The main features are: between skeleton ceramic filling elements in situ reinforced concrete beams are prepared during the construction of the relatively narrowly spaced RC beamed slabs. In the studied cases mainly due to the pure workmanship of concrete construction, and/or due to some other influencing factors the bottom surface of the ceilings of such construction systems delaminated. The first underneath sight of such failures are usually frightening, and if an inexperienced person views the result, the statement of the slab to be life dangerous, and it should be reconstructed may be made. At the same time the slab may be saved, and the repair is much more cost eective than demolishing and reconstructing the structure

Power-law tails from multiplicative noise

We show that the well-known Langevin equation, modeling the Brownian motion and leading to a Gaussian stationary distribution of the corresponding Fokker-Planck equation, is changed by the smallest multiplicative noise. This leads to a power-law tail of the distribution at large enough momenta. At finite ratio of the correlation strength for the multiplicative and additive noise the stationary energy distribution becomes exactly the Tsallis distribution.Comment: 4 pages, LaTeX, revtex4 style, 2 figure

Phase field theory of crystal nucleation in hard sphere liquid

The phase field theory of crystal nucleation described in [L. Granasy, T. Borzsonyi, T. Pusztai, Phys. Rev. Lett. 88, 206105 (2002)] is applied for nucleation in hard--sphere liquids. The exact thermodynamics from molecular dynamics is used. The interface thickness for phase field is evaluated from the cross--interfacial variation of the height of the singlet density peaks. The model parameters are fixed in equilibrium so that the free energy and thickness of the (111), (110), and (100) interfaces from molecular dynamics are recovered. The density profiles predicted without adjustable parameters are in a good agreement with the filtered densities from the simulations. Assuming spherical symmetry, we evaluate the height of the nucleation barrier and the Tolman length without adjustable parameters. The barrier heights calculated with the properties of the (111) and (110) interfaces envelope the Monte Carlo results, while those obtained with the average interface properties fall very close to the exact values. In contrast, the classical sharp interface model considerably underestimates the height of the nucleation barrier. We find that the Tolman length is positive for small clusters and decreases with increasing size, a trend consistent with computer simulations.Comment: 7 pages, 7 figure

Disease course, frequency of relapses and survival of 73 patients with juvenile or adult dermatomyositis

Objective Our aim is to present the disease course, frequency of relapses and survival of juvenile and adult dermatomyositis (JDM/DM) patients. Methods Analysis was performed using data on 73 patients. The median follow-up for 38 JDM patients was 32 months and 78 months for 35 adult DM patients. Results 23/38 JDM patients (60%) had monophasic, 12/38 (31.6%) had polycyclic and 3138 (7.9%) had chronic disease. Among children treated only with glucocorticoids, 12/20 (60%) had monophasic and 8/20 (40%) had polycyclic disease. 10/17 (58.8%) children, who required second-line immunosuppressive agents, had monophasic and 4/17 (23.5%) had polycyclic disease. 18/35 DM (51.4%) patients had monophasic, 13/35 (37.1%) had polycyclic, 1/35 (2.9%) had chronic disease and 3135 (8.6%) had fulminant myositis. Among DM patients requiring only glucocorticoids, 12/20 (60%) were monophasic and 8/20 (40%) were polycyclic. In patients requiring second-line immunosuppressive agents, 6/15 patients (40%) had monophasic and 5/15 (33.3%) had polycyclic disease. Among patients with polycyclic disease, the risk of relapse was higher during first year than later in the disease course. None of the JDM patients have died, while 4 disease-specific deaths occurred in adult patients. There was no significant difference between the survival of JDM and DM patients. Discussion There was no correlation between relapse-free survival and the initial therapeutic regimen. Many of our patients had polycyclic or chronic disease. As relapses can occur after a prolonged disease-free interval, patients should be followed for at least 2 years. Although we found a favourable survival rate, further investigations are needed to assess functional outcome

Additive decomposability of functions over abelian groups

Abelian groups are classified by the existence of certain additive decompositions of group-valued functions of several variables with arity gap 2.Comment: 17 page