Internal localized eigenmodes on spin discrete breathers in antiferromagnetic chains with on-site easy axis anisotropy

We investigate internal localized eigenmodes of the linearized equation around spin discrete breathers in 1D antiferromagnets with on-site easy axis anisotropy. The threshold of occurrence of the internal localized eigenmodes has a typical structure in parameter space depending on the frequency of the spin discrete breather. We also performed molecular dynamics simulation in order to show the validity of our linear analysis.Comment: 4 pages including 5 figure

Biodegradable polymeric prodrugs of naltrexone

The development of a biodegradable polymeric drug delivery system for the narcotic antagonist naltrexone may improve patient compliance in the treatment of opiate addiction. Random copolymers consisting of the ¿-amino acids N5-(3-hydroxypropyl--glutamine and -leucine were synthesized with equimolar initial monomer feeds. The molecular weight of this chemical carrier was determined by viscometry and wide-angle light scattering. In order to get selective covalent coupling of drug to polymer the 3-acetate derivative and the 14-acetate derivative of naltrexone were synthesized and characterized by NMR. Hydrolytic conversion of each monoacetate to parent drug was monitored by HPLC and the rate constant was determined. Both derivatives were coupled via hydrolytically labile carbonate linkages to the polymer hydroxyl groups. The drug conjugates were prepared as particles of various size ranges between 20 and 350 ¿. In vitro studies in phosphate-buffered saline (pH 7.4) demonstrated a release rate dependence on particle size. Nearly constant plasma levels of naltrexone were obtained for one month after subcutaneous injection in rats

Wettability and ζ potentials of a series of methacrylate polymers and copolymers

Polymers and copolymers of different methacrylates were synthesized and coated on glass slides. The surfaces of the polymer films were characterized by their water contact angles and potentials using the Wilhelmy plate technique and streaming potential measurements, respectively. From contact-angle measurements information was also obtained about mobility of surface polymer chains. Receding contact angles of methyl methacrylate (MMA) copolymers containing hydrophilic or charged units were decreased as compared to the MMA homopolymer. When charged hydroxyethyl methacrylate (HEMA) copolymers were compared with the HEMA homopolymer, the advancing contact angles increased, probably due to reorientation of surface polymer chains. The receding contact angles of poly(alkyl methacrylates) first increased and then decreased with increasing side-chain lengths. These changes were related to the mobility of the different polymers. Incorporation of positively or negatively charged groups in MMA or HEMA polymers accordingly changed the potential of the polymers

Adriamycin loading and release characteristics of albumin-heparin conjugate microspheres

Biodegradable ion-exchange microspheres, prepared from a prefabricated conjugate of albumin and heparin were investigated as carriers for adriamycin. The ion-exchange microspheres could be loaded with adriamycin giving payloads up to 33% w/w, depending on the heparin content of the conjugate. In vitro adriamycin release depended on the ionic strength of the release medium. In ion containing media, for instance saline, 90% of the drug was released within 45 min, whereas in non-ionic media, such as distilled water, only 30% was released. Drug release profiles could be modelled by combining ion-exchange kinetics and diffusion controlled drug release models

Heparin-containing block copolymers, Part I: Surface characterization

Newly synthesized heparin-containing block copolymers, consisting of a hydrophobic block of polystyrene (PS), a hydrophilic spacer-block of poly(ethylene oxide) (PEO) and covalently bound heparin (Hep) as bioactive block, were coated on aluminium, glass, polydimethylsiloxane (PDMS), PS or Biomer substrates. Surfaces of coated materials were characterized by transmission electron microscopy (TEM), contact angle measurements and X-ray photoelectron spectroscopy for chemical analysis (XPS). It was demonstrated by TEM that thin films of PS-PEO and PS-PEO-Hep block copolymers consisted of heterogeneous microphase separated structures. Using sessile-drop and Wilhelmy plate dynamic contact angle measurements, insight was provided into the hydrophilicity of the surfaces of the coatings. Measurements with hydrated coatings of PS-PEO and PS-PEO-Hep block copolymers revealed that the surfaces became more hydrophilic during immersion in water, due to relaxation/reorientation, or swelling of PEO or PEO-Hep domains, respectively. XPS results for PS, PEO, heparin and PS-PEO as powder agreed well with qualitative and quantitative predictions. XPS results for films of PS-PEO and PS-PEO-Hep block copolymers showed enrichments of PEO in the top layers of the coatings. This effect was more pronounced for hydrated surfaces. Only small amounts of heparin were detected at the surface of coatings of PS-PEO-Hep block copolymers

Searching for Ground Truth: a stepping stone in automating genre classification

This paper examines genre classification of documents and its role in enabling the effective automated management of digital documents by digital libraries and other repositories. We have previously presented genre classification as a valuable step toward achieving automated extraction of descriptive metadata for digital material. Here, we present results from experiments using human labellers, conducted to assist in genre characterisation and the prediction of obstacles which need to be overcome by an automated system, and to contribute to the process of creating a solid testbed corpus for extending automated genre classification and testing metadata extraction tools across genres. We also describe the performance of two classifiers based on image and stylistic modeling features in labelling the data resulting from the agreement of three human labellers across fifteen genre classes.

Experimental constraints on the parameter space of the next-to-minimal supersymmetric standard model at LEP 2

We search for the neutral Higgs sector of the next-to-minimal supersymmetric standard model at LEP 2. At the tree level any experimental constraints on $\tan \beta$ cannot be set by the Higgs search at LEP 2 with $\sqrt{s}$ = 175 GeV, whereas at LEP 2 with $\sqrt{s}$ = 192 GeV $\tan \beta$ can be set by an experimental constraint. Furthermore the tree level parameter space of the model can be completely explored by the Higgs search at LEP 2 with $\sqrt{s}$ = 205 GeV. Radiative corrections both to the neutral Higgs boson masses and to the relevant couplings for the scalar Higgs productions give large contributions to the production cross sections of the scalar Higgs bosons at the tree level. The tree level situation at LEP 2 with $\sqrt{s}$ = 192 GeV as well as with $\sqrt{s}$ = 205 GeV can be drastically changed by these effects. We expect that a small region of the 1-loop level parameter space of the model via the scalar Higgs production can be explored by the Higgs search at LEP 2.Comment: 14 pages (3 figures are included

Probing orographic controls in the Himalayas during the monsoon using satellite imagery

The linkages between the space-time variability of observed clouds, rainfall, large-circulation patterns and topography in northern India and the Himalayas were investigated using remote sensing data. The research purpose was to test the hypothesis that cloudiness patterns are dynamic tracers of rainstorms, and therefore their temporal and spatial evolution can be used as a proxy of the spatial and temporal organization of precipitation and precipitation processes in the Himalayan range during the monsoon. The results suggest that the space-time distribution of precipitation, the spatial variability of the diurnal cycle of convective activity, and the terrain (landform and altitudinal gradients) are intertwined at spatial scales ranging from the order of a few kms (1–5km) up to the continental-scale. Furthermore, this relationship is equally strong in the time domain with respect to the onset and intra-seasonal variability of the monsoon. Infrared and microwave imagery of cloud fields were analyzed to characterize the spatial and temporal evolution of mesoscale convective weather systems and short-lived convection in Northern India, the Himalayan range, and in the Tibetan Plateau during three monsoon seasons (1999, 2000 and 2001). The life cycle of convective systems suggests landform and orographic controls consistent with a convergence zone constrained to the valley of the Ganges and the Himalayan range, bounded in the west by the Aravalli range and the Garhwal mountains and in the East by the Khasi Hills and the Bay of Bengal, which we call the Northern India Convergence Zone (NICZ). The NICZ exhibits strong night-time activity along the south-facing slopes of the Himalayan range, which is characterized by the development of short-lived convection (1–3h) aligned with protruding ridges between 1:00 and 3:00 AM. The intra-annual and inter-annual variability of convective activity in the NICZ were assessed with respect to large-scale synoptic conditions, monsoon activity in the Bay of Bengal, and the modulating role of orography. Empirical orthogonal function (EOF) and canonical correlation (CC) analysis suggest that joint modes of variability of monsoon weather and topography, which we call orographic land-atmosphere interactions, modulate the space-time variability of cloudiness in the region. Finally, scaling analysis of cloudiness suggests three different scaling regimes of orographic land-atmosphere interactions: 1) a synoptic-scale regime (≥70-80km); 2) an orographic meso–β regime (30–70km) associated with the succession of wide valleys and bulky terrain features; and 3) an orographic meso–α regime (≤30km) associated with the complex succession of protruding south-facing ridges and narrow valleys that characterize the Himalayan foothills between altitudes of 3000 and 5000m elevations

Calculation of cumulative damage of tetrapod armor layer

In the performance-based design of a breakwater armor layer, it is often necessary to calculate its damage accumulated over the life cycle of the breakwater. Two methods for calculating the cumulative damage have been proposed; one by Melby and Kobayashi in 1998 and the other by Hanzawa et al. in 1996. In this paper, comparison is made between the two methods for a Tetrapod armor layer. For the damage progression of Tetrapod armor units, hydraulic experiments are made. In the case where a severe damage occurs at the beginning of the life cycle of the breakwater, the two methods do not show significant difference, but in general the latter predicts a larger cumulative\ud damage than the former. For a Tetrapod armor layer, it is recommended to use the average of the two methods