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Abstract
The thermal stability, kinetics and glass forming ability of an Fe77C5B4Al2GaP9Si2 bulk amorphous alloy have been studied by differential scanning calorimetry. The activation energy, frequency factor and rate constant corresponding to the multiple crystallization steps were determined by the Kissinger method. X-ray diffraction and transmission electron microscopy studies revealed that the crystallization starts with the primary precipitation of α-Fe from the amorphous matrix. The kinetics of nucleation of the α-Fe nanoparticles was investigated by two different methods, i.e. isothermal annealing and continuous heating after partial annealing.
Due to its nearly 1.5 million ha extension and the aimed fine mapping resolution, classical vegetation mapping was not suitable method to prepare the habitat map of Duna-Tisza köze region (Hungary). We developed a novel mapping method. By this method the actual status of more than 12,000 patches of semi-natural vegetation was recorded, documented previously as grasslands, wetlands, open forests and grasslands with scattered trees and shrubs in the middle of the 1980s. A digital layer of 272,387 ha at 1 : 25,000 resolution was created as the background of the analysis. Vegetation type was classified at 46,930 points in the mapping area. The collaboration of 59 colleagues resulted in the development of the digital geographical database of the study area (D-TMap GIS Point database). One-third of the data relies on field data, while the other two-thirds on satellite interpretation. Landscape pattern and the accuracy of the statistical data of the habitats, generated from the point database, are improved by the polygonised version of the point database (D-TMap GIS Polygon database). In this paper we show how the GIS Point database was generated, and summarise the ecological content, availability, and limitation of the derived point and polygon based actual habitat maps. Analysis of the database and the landscape scale pattern of the habitats are discussed in a further paper.
Regional habitat pattern of the Danube-Tisza Interfluve in Hungary, I
The landscape structure and habitat pattern; the fen and alkali vegetation
As a result of the groundwater level decline observed in the last two decades and the socio-economic changes, we assume that a drastic alteration begins in the landscape pattern of Danube-Tisza Interfluve (Duna-Tisza köze, Kiskunság s. l.). It demands the documentation of the actual state of vegetation in this region, and its quantitative analysis, as well. In the first of the two articles presenting our results we discuss the regional habitat-pattern of the landscape, the background factors determining it, and the basic features of fen and alkali vegetation. In the second part, this will be completed by the sand, riverine and steppe vegetation and the data on habitat-devastation on the regional scale.During our study we determined the Danube-Tisza Interfluve (with a total extension of nearly 1.4 million ha) in the geographical sense. The analysis of the present habitat-pattern of the region was based on data of the actual (1996–2000) habitat map of Danube-Tisza Interfluve (Molnár et al. 2000, Biró et al. 2000) and on our experience during the field survey. We compared our data to surface-geographical, pedological and hydrological works, to maps from the 18–19th centuries on land-use, to botanical studies accomplished in the 19–20th centuries and to the results of other related sciences. The quantitative analysis of the vegetation pattern was carried out considering the vegetation subregions.About half (49.4%) of the surveyed, not cultivated habitats of the Danube-Tisza Interfluve is in a natural, semi-natural state, and nearly a quarter of them (23.8%) is essentially disturbed or under deep human impact. During the one- and-a-half decades between the topographical mapping of the mid-1980s and the habitat mapping (D-TMap), 14.7% of the surveyed habitats disappeared, and appr. 12.1% is now in the state of regeneration after the disturbance of the distant or the recent past. Today, fen vegetation (including the vegetation of non-alkali swamps and uncharacteristic fen vegetation that is drying out at present) is predominant among the studied habitats of the region (it covers 95,135 ha), that is followed by alkali vegetation with an extension of about half of the former one (47,226 ha).The joint vegetation categories (sand, fen, alkali and riverine vegetation) of the region compose vegetation zones running north and south. So, on the two sides of the Sand Ridge vegetation zones dominated by fen habitats lie, which is followed by the zone of alkali habitats; finally, the riverine vegetation prevails along the rivers Danube and Tisza. From the abiotic factors determining these zones we emphasised the hydrodynamic characteristics — that play recently the most essential role. As a result of the analysis of landscape pattern, it became obvious, that the natural habitats — similarly to the hydraulically continuous groundwater flow systems — of the Danube-Tisza Interfluve compose hierarchical systems, basically on three different levels (on the local, intermediate and regional scale). In this point of view, those areas are considered as a certain system, where the underground water flow (recharge, throughflow and discharge) forms a uniform flow system. We approached to the survey of the actual vegetation of the Danube-Tisza Interfluve with this viewpoint of the hierarchically structured habitat pattern.
Regional habitat pattern of the Danube-Tisza Interfluve in Hungary II
The sand, the steppe and the riverine vegetation, degraded and regenerating habitats, regional habitat destruction
The increased endangerment and rapid devastation of the vegetation on the Danube-Tisza Interfluve are quite complex processes that can be approached from a manifold ways. One of the most important factors having influenced the vegetation in the recent past is the decline of the groundwater-level, the extent of which is well known and the reasons for that have been investigated for a long time. However, only few have studied its dramatic effect on the vegetation outside the local scale. In the first part of our bipartite article we discuss the regional habitat-pattern of the landscape, the background factors determining it, and the basic features of fen and alkali vegetation (Biró et al. 2007). In this second part, this will be completed by the sand, riverine and steppe vegetation and the data on habitat devastation on the regional scale. The analysis of the present habitat-pattern of the region was based on data of the actual (1996–2000) habitat map of Danube-Tisza Interfluve (Molnár et al. 2000, Biró et al. 2003) and on our experiences during the field survey. The quantitative analysis of the vegetation pattern was carried out considering the vegetation subregions. Our aim is to expose the actual state of the landscape, the vegetation and the rapid devastation of the natural habitats, by quantifying the current processes.Our results demonstrate that the extension of those habitats on the Danube-Tisza Interfluve that were not under cultivation in the 1980s has decreased drastically, by 40,074 ha (approx. 15%). The main reasons for grassland devastations are ploughing, afforestation, the invasion of shrubs and trees, the building in activity and the establishment of open water surfaces. The most serious decline in the recent past was observed in the case of fen vegetation: the decrease of its extension was estimated to be 10–11%. More than half of the habitats disappeared as a result of ploughing and grassland-devastation due to urbanisation (building in, development of infrastructure, etc.) was covered by fen vegetation, while about a quarter of them consisted of alkali habitats. Sand areas mostly decline because of the spontaneous invasion of alien species and afforestation, which led to the devastation of approx. 4% of the natural and disturbed sand vegetation. Astonishing is the fact that the total extension of the more-or-less disturbed or devastated habitats altogether comprise roughly half (49%) of the actually mapped vegetation patches of the Interfluve (137,908 ha). By summing up the areas of the most frequent habitat types of the vegetation subregions, it became evident that the grasslands, ploughed in the past 15 years, are among the first five most spacious habitat types in all subregions.
Abstract
Sugar esters (SEs) have a wide range of hydrophilic-lipophilic balance (HLB) values (1–16) and hence can be applied as surfactants or as solubility or penetration enhancers. They can be used for hot melt technology and solvent method which are frequently applied techniques to preparation of solid dispersions. In this study drug-SE products were prepared by physical mixing, melt technology and solvent methods. The products were investigated by DSC, X-ray powder diffraction and dissolution tests. Diclofenac sodium (DS) as model drug and two SEs, P1670 (HLB=16) and S970 (HLB=9) were used for the preparation of the products. DSC curves revealed considerable melting range and enthalpy decreases for the DS-SE products. The dissolved drug molecules broke down the structures of the SEs but were not built into the crystalline phase of the carrier. The melt technology led to a solid dispersion while in the case of the solvent methods the DS was in molecularly dispersed form which resulted in faster dissolution. The drug release was influenced by the structures resulting from the various treatments, by the HLB and by the gel-forming behaviour of the SEs.
Abstract
A study was made of the possibilities of gradually decreasing the concentration of the toxic organic solvent in the process of microsphere preparation. Ammonio methacrylate copolymer-based microspheres were prepared by spray drying or conventional solvent evaporation techniques, and compared. The formulations were designed by varying the preparation methods and the concentrations of four polar cosolvents as independent variables. DSC was used to study the relationship between the changes in the independent variables and three of the main thermal events of the microspheres. Raman spectroscopy was used to investigate and confirm the possible interactions between drug and copolymer. Appropriate choice of the independent variables led to the molecularly dispersed drug in the polymer matrix. It was demonstrated that only the nature of the preparation method caused significant variations in the structure and thermal behaviour of the microspheres.
Abstract
In pharmaceutical practice it is important and useful to know the crystallinity of materials and to monitor it during formulation development, production processes and storage. The purpose of this study was to assess the quantitative capability of DSC for determining crystallinity in crystalline/amorphous powder mixtures and to compare the accuracy of the DSC method with that of conventional powder X-ray diffraction. Alpha-lactose monohydrate was chosen as the model material. On the basis of this study it can be concluded, that DSC method can be applied safely for semiquantitative evaluation of the crystallinity of lactose samples consisting of an amorphous content higher than 20%.
