The origin of interparticle potential of electrorheological fluids

The particles of electrorheological fluids can be modelled as dielectric spheres (DS) immersed in a continuum dielectric. When an external field is applied, polarization charges are induced on the surfaces of the spheres and can be represented as point dipoles placed in the centres of the spheres. When the DSs are close to each other, the induced charge distributions are distorted by the electric field of the neighbouring DSs. This is the origin of the interaction potential between the DSs. The calculation of this energy is very time consuming, therefore, the DS model cannot be used in molecular simulations. In this paper, we show that the interaction between the point dipoles appropriately approximates the interaction of DSs. The polarizable point dipole model provides better results, but this model is not pair-wise additive, so it is not that practical in particle simulations.Comment: 10 pages, 5 figure

Report of review of St Stephen’s Children’s Centre, Newham: services for children aged up to 3 years

Formation of surface depressions is a significant geological hazard. Prediction of future sinkholes in buried karstic areas needs knowledge about the subsurface. In order to determine the varying topography of the karstifiable bedrock we carried out multielectrode measurements. Due to the hard field conditions, the bedrock depth could not be detected. The resistivity anomalies in some places had a seasonal variation (low-resistivity in springtime, high-resistivity in the end of summer); therefore we interpreted the springtime resistivity lows as indicators of locations with high water content, that is as high porosity, saturated with water. At the same time, when pushing the current- and potential electrodes into the ground, we discovered a regularity in the areal distribution of the soil's rock debris content. Therefore we carried out a systematic electrode-pricking experiment, and categorized the soil's "toughness" corresponding to soft penetration, scratching or blockage within the upper 30 cm. We have found a close relationship between the locations of resistivity- and the soil's toughness extremes. From some epikarstic features we think that high "pricking probe" values indicate smaller depths of the bedrock. The corresponding (springtime) resistivity minima may indirectly indicate more or less collapsed horsts of the carbonate rock

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

Mass and orbit constraints of the gamma-ray binary LS 5039

We present the results of space-based photometric and ground-based spectroscopic observing campaigns on the gamma-ray binary LS 5039. The new orbital and physical parameters of the system are similar to former results, except we found a lower eccentricity. Our MOST-data show that any broad-band optical photometric variability at the orbital period is below the 2 mmag level. Light curve simulations support the lower value of eccentricity and imply that the mass of the compact object is higher than 1.8 solar masses.Comment: 2 pages, 1 figure (with 2 panels); to be published in the Proceedings: From Interacting Binaries to Exoplanets: Essential Modeling Tools, IAU Symposium 282 (18-22 July, 2011, Tatranska Lomnica, Slovakia

A galgahévízi láprét talajtani, hidrológiai és szedimentológiai vizsgálata

Napjainkban fokozott figyelem irányul a vizes élőhelyek felé. Hazánkban jelentősen lecsökkent a területük, szigetszerűvé váltak, éppen ezért, a természetes közegben betöltött egyedülálló ökológiai szerepüknek köszönhetően egyre inkább az érdeklődés és a kutatások középpontjába kerülnek (Ángyán et al. 2004). Galgahévíz a Gödöllői-dombság és az észak-alföldi hordalékkúp síkság határán helyezkedik el, a Galga-patak mentén. A területet Ny-ról határolja a Sósi-patak, amely egykor a lápréten keresztül jutott a Galga-patakba. A láprét természeti értékeinek degradációja (amelyet korábban a legeltetés és a kaszálás miatt jelentős volt) az 1990-es évek végén felerősödött, eltűnőben vannak egyes, természetvédelmi szempontból értékes növényfajok és társulások. Célunk az volt, hogy feltárjuk ezen degradációs folyamatok talajtani, hidrológiai, okait, a láprétet veszélyeztető tényezőket. A láprét kialakulását meghatározó egyik, talán a legfontosabb tényező a víz, ezért fennmaradásához alapvetően fontos a vízutánpótlás biztosítása. A láprét vízháztartásának, vízutánpótlásának megismerése, megértése megalapozhatja a revitalizációs terveket. A láprét kutatása az 1990-es évek végén kezdődött, azóta számos publikáció született az itt feltárt eredményekről

High-Velocity Features of Calcium and Silicon in the Spectra of Type Ia Supernovae

"High-velocity features" (HVFs) are spectral features in Type Ia supernovae (SNe Ia) that have minima indicating significantly higher (by greater than about 6000 km/s) velocities than typical "photospheric-velocity features" (PVFs). The PVFs are absorption features with minima indicating typical photospheric (i.e., bulk ejecta) velocities (usually ~9000-15,000 km/s near B-band maximum brightness). In this work we undertake the most in-depth study of HVFs ever performed. The dataset used herein consists of 445 low-resolution optical and near-infrared (NIR) spectra (at epochs up to 5 d past maximum brightness) of 210 low-redshift SNe Ia that follow the "Phillips relation." A series of Gaussian functions is fit to the data in order to characterise possible HVFs of Ca II H&K, Si II {\lambda}6355, and the Ca II NIR triplet. The temporal evolution of the velocities and strengths of the PVFs and HVFs of these three spectral features is investigated, as are possible correlations with other SN Ia observables. We find that while HVFs of Ca II are regularly observed (except in underluminous SNe Ia, where they are never found), HVFs of Si II {\lambda}6355 are significantly rarer, and they tend to exist at the earliest epochs and mostly in objects with large photospheric velocities. It is also shown that stronger HVFs of Si II {\lambda}6355 are found in objects that lack C II absorption at early times and that have red ultraviolet/optical colours near maximum brightness. These results lead to a self-consistent connection between the presence and strength of HVFs of Si II {\lambda}6355 and many other mutually correlated SN~Ia observables, including photospheric velocity.Comment: 48 pages (22 of which are tables), 15 figures, 5 tables, re-submitted to MNRAS (after first referee report

Searching for the expelled hydrogen envelope in Type I supernovae via late-time H-alpha emission

We report the first results from our long-term observational survey aimed at discovering late-time interaction between the ejecta of hydrogen-poor Type I supernovae and the hydrogen-rich envelope expelled from the progenitor star several decades/centuries before explosion. The expelled envelope, moving with a velocity of ~10 -- 100 km s$^{-1}$, is expected to be caught up by the fast-moving SN ejecta several years/decades after explosion depending on the history of the mass-loss process acting in the progenitor star prior to explosion. The collision between the SN ejecta and the circumstellar envelope results in net emission in the Balmer-lines, especially in H-alpha. We look for signs of late-time H-alpha emission in older Type Ia/Ibc/IIb SNe having hydrogen-poor ejecta, via narrow-band imaging. Continuum-subtracted H-alpha emission has been detected for 13 point sources: 9 SN Ibc, 1 SN IIb and 3 SN Ia events. Thirty-eight SN sites were observed on at least two epochs, from which three objects (SN 1985F, SN 2005kl, SN 2012fh) showed significant temporal variation in the strength of their H-alpha emission in our DIAFI data. This suggests that the variable emission is probably not due to nearby H II regions unassociated with the SN, and hence is an important additional hint that ejecta-CSM interaction may take place in these systems. Moreover, we successfully detected the late-time H-alpha emission from the Type Ib SN 2014C, which was recently discovered as a strongly interacting SN in various (radio, infrared, optical and X-ray) bands.Comment: 8 pages, 7 figures, accepted in Ap