317 research outputs found
KĂsĂ©rleti Ă©s elmĂ©leti kutatások fotofizikai folyamatok oldĂłszerfĂĽggĂ©sĂ©nek általánosabb leĂrására = Experimental and theoretical examinations for better understanding of solvent dependence of photophysical processes
A zárĂłjelentĂ©sben bemutatott kutatásokban több modellrendszeren vizsgáltuk az oldĂłszer kĂĽlönbözĹ‘ tulajdonságainak - Ăgy polaritásának, viszkozitásának Ă©s hidrogĂ©nhĂd-kötĹ‘ kĂ©pessĂ©gĂ©nek - hatását a fotofizikai rendszer viselkedĂ©sĂ©re. A polaritás-fĂĽggĂ©st a Lippert-Mataga formalizmussal Ă©rtelmeztĂĽk, az effektus segĂtsĂ©gĂ©vel meg tudtuk határozni több 4-amino-benzonitril származĂ©k, az N-fenil-pirol, a 4-(dimetilamino)-piridin Ă©s az utĂłbbi molekula hidrogĂ©nhidas komplexĂ©nek gerjesztett állapotĂş dipĂłlusmomentumát is. A komlexált molekula esetĂ©ben az oldĂłszer polaritásának növelĂ©se a gerjesztett állapot jellegĂ©nek megváltozását indukálta. A gerjesztett állapotĂş folyamatok termodinamikájának Ă©s kinetikájának kvantitatĂv elemzĂ©se lehetĹ‘vĂ© tette a hasonlĂł jellegű, alapállapotban is lejátszĂłdĂł folyamatok sebessĂ©gĂ©nek becslĂ©sĂ©t, valamint az eredmĂ©nyeink alapján felmerĂĽlt annak a lehetĹ‘sĂ©ge is, hogy a hidrogĂ©nhidas komplexkĂ©pzĹ‘dĂ©s egyáltalán nem tekinthetĹ‘ elemi reakciĂłnak. Megmutattuk, hogy az oldat viszkozitása jelentĹ‘sen befolyásolhatja a gerjesztett állapotĂş folyamatokat, egyrĂ©szt a nagy amplitĂşdĂłjĂş relaxáciĂłs mozgások gátlásával, másreszt az oldĂłszerburok átrendezĹ‘dĂ©sĂ©nek fĂ©kezĂ©sĂ©vel, ennek eredmĂ©nyekĂ©ppen szĂ©lsĹ‘sĂ©gesebb esetekben meglepĹ‘ kinetikai Ă©s fotofizikai jelensĂ©geket is tapasztalhatunk. | In our examinations presented here, the properties of several model systems are elucidated as the function of solvent polarity, viscosity as well as hydrogen bond donor properties. The influence of the polarity was described by the Lippert-Mataga equation, and the excited state dipole moments were calculated for 4-aminobenzonitril derivatives, for N-phenylpyrol, for 4-(dimethylamino)pyridine and its hydrogen-bond complexed derivative. The increase of the solvent polarity induces a change in the nature of the intramolecular charge transfer singlet excited species in the last case. Quantitative analysis of the thermodynamics and kinetics of the excited state hydrogen-bond forming processes made possible to estimate rate of the analogous ground-state reactions, as well as to suppose the assumption that the reaction in question is not an elementary process at all. The viscosity of the solvent was shown a crucial factor influencing the excited state processes by hindering the large amplitude intramolecular relaxation motions, as well as by slowing down the solvent relaxation processes causing in extreme cases surprising kinetic and photophysical feature
A biodiverzitás monitorozása homoki élőhelyeken a Duna-Ipoly Nemzeti Park Igazgatóság területén = Monitoring of sand steppe species and habitats in the administrative area of the Duna-Ipoly National Park Directorate
A quarter of Hungary’s calcareous sand vegetation is in the administrative area of the Danube–Ipoly National Park Directorate. Therefore, monitoring sandy habitats and species is important. Monitoring is done mainly by the nationally coordinated Hungarian National Biodiversity Monitoring System (HNBMS). Estimating the population size of plant and animal species monitored by the HNBMS in the administrative area of the national park directorate. Our results show that the number of Bulbocodium versicolor, Colchicum arenarium, Dianthus diutinus, Ephedra distachya and Iris arenaria are 2 700, 200 000, 13 500, 70 000 and 70 000 individuals, respectively. Monitoring results of European Ground Squirrel (Spermophilus citellus) support the hypothesis that areas with short grass can hold more dense populations. However, such areas are found on airfields, which are intensively mown or grazed. The densest population among the studied areas was at Dunakeszi
airfield. The most extensive populations of the European Ground Squirrel live in the region of Táborfalva military training area, and in the region of Ürbő. The monitoring of Carabus hungaricus showed that the choice of habitat it prefers exclusively open habitat types. Within the steppic
vegetation, this beetle is associated with the more dense tall grass type of vegetation. In practice it means that the habitat of Carabus hungaricus would be turned by natural succession into a scrubby or a wooded habitat type. Succession can be managed by grazing, but the management of
the grasslands can easily lead to a change in the habitat into a less dense short grass type, which is insufficient for the beetle. Our own experience is that if grass cover is low, the predation pressure rises, which can be seen in the high number of injured beetles. Optimising grazing is crucial for the survival of Carabus hungaricus in an area.
Vegetation mapping near Nagykőrös showed that the steppic oak vegetation native to this area is fragmented. Habitat fragments are islands of native vegetation surrounded by
plantations of non-native and invasive trees. These plantations are the main spreading hotspots of herbaceous and arboreal invasive plants. Data gathered with monitoring is used primary in the daily work, planning and
consulting of, for example, forest managers, environmental officers and land managers, but data is also used to help scientific research. To preserve threatened, endemic species, appropriate treatment of the habitats are needed. The funding of European Union nature conservation budgets helps us to manage areas and treat species to preserve a good nature conservation status
Adatok a Baláta-tói természetvédelmi terület futóbogárfaunájához (Coleoptera: Carabidae) = Carabidae Data on the Baláta-to Nature Protection Area in Hungary
In the following paper data is given about 45 speci-
es of ground beetles collected - mostly - with pit-fall traps in
the Hungarian Baláta-Lake Nature Reserve Area, in three
plant associations (Quercetum; Alnetum; Salicetum). The
highest diversity of ground beetles was measured in the
Salicetum plant association, and the lowest in the Quercetum
association, although significant difference could not bee
shown between the Salicetum and the Alnetum. Our
investigations showed that the wooden habitats have more
equal environment conditions than the Salicetum for ground
beetles. This could be shown by the higher number of
collected specimen and the lower number of species in
wooden habitats (K-strategy)
HelyesĂrás
Az Osiris KiadĂł igen Ă©rdekes Ă©s már sokak által várt vállalkozásra szánta el magát. Tolcsvai Nagy Gábor sorozatának ötlete a magyar nyelv minden eddiginĂ©l rĂ©szletesebb bemutatása egy tĂzkötetes kĂ©zikönyvsorozatban. A 2004-ben megjelent ,HelyesĂrás’ a ,Magyar Nyelv KĂ©zikönyvtára’ sorozat elsĹ‘ tagja
Consonant lenition inside and outside the “minimal foot” : A Strict CV Phonology analysis
English represents stress-sensitive consonant lenition systems, in which the onsets of stressed syllables (as well as word-initial consonants) tend to resist diachronic lenition, resulting in synchronic alternations between foot-initial and foot-internal variants. However, there is empirical evidence that a further distinction needs to be drawn between two subtypes of foot-internal positions: one which is weak proper, included within a bimoraic domain (corresponding to the “minimal foot” in prosodic approaches); and a less weak (“semi-weak”) position outside that minimal domain. Crucially, lenition outside the domain implies lenition within, and no cases of lenition in semi-weak only are on record. The paper uses the representations of Strict CV Phonology to capture the equivalence of two forms of the “minimal foot” (the CVCV sequence and the long-vowelled heavy syllable) and to connect this “bimoraicity” of the domain to the implications in consonant lenition, a benefit moraic theory does not offer. At the same time, it properly predicts the non-existence of the unattested lenition pattern
Égésekben szerepet játszó OH-gyök és H-atom reakciók kinetikája = The kinetics of OH-radical and H-atom reactions of importance in combustion
Az OH reakciĂłk kinetikája: Az OH + CH3 sokcsatornás reakciĂłt nagyobb nyomásoknál lĂ©zer villanĂłfĂ©ny fotolĂzis technikával, kisebb nyomásoknál gyorsáramlásos mĂłdszerrel vizsgáltuk. A hĹ‘mĂ©rsĂ©klet fĂĽggvĂ©nyĂ©ben meghatároztuk a bruttĂł sebessĂ©gi egyĂĽtthatĂłt. Kimutattuk, hogy a 1CH2 + H2O termĂ©kekhez vezetĹ‘ folyamat a legfontosabb csatorna, amelynek elágazási arányát 0.7 - 0.9-nek találtuk. Az OH + alkil-formiátok vizsgálata során azt találtuk, hogy a sebessĂ©gi egyĂĽtthatĂł jelentĹ‘sen fĂĽgg az alkil csoporttĂłl. KĂsĂ©rleti Ă©s elmĂ©leti vizsgálatokban összevetettĂĽk a formiát- Ă©s a formil-csoport reaktivitását az OH gyökkel lejátszĂłdĂł reakciĂłkban. ElmĂ©leti számĂtásokkal Ă©rtelmezni tudtuk a formil csoport 2 nagyságrenddel nagyobb reaktivitását. Szabadgyök kĂ©pzĹ‘dĂ©shĹ‘k meghatározása: Az u.n. kinetikai egyensĂşlyi mĂłdszert alkalmazva, brĂłmozási reakciĂłk vizsgálatával meghatároztuk szabadgyökök kĂ©pzĹ‘dĂ©shĹ‘it. A ?harmadik fĹ‘tĂ©tel? eljárással nyertĂĽk a CH2OH (-17.6 - 2.0 kJ mol-1), a CH3C(O)CH2 (-28 kJ mol-1) Ă©s a CHClBr(140 - 4 kJ mol-1) gyökök kĂ©pzĹ‘dĂ©si entalpiáját. Szabadgyökök termodinamikai adatbázisának fejlesztĂ©se: Irodalmi adatok kritikai elemzĂ©sĂ©vel (Ă©s saját kutatási eredmĂ©nyek felhasználásával) megkezdtĂĽk szabadgyökök termodinamikai adatbázisának kifejlesztĂ©sĂ©t. Eddig 11 gyök adatlapjait publikáltuk. | The kinetics of OH reactions: The multichannel OH + CH3 reaction was studied at high pressures by the laser flash photolysis technique and at low pressures by the discharge flow method. The overall rate coefficients were determined as a function of temperature. It was shown that the reaction leading to 1CH2 + H2O products is the dominant channel for which the branching ratios of 0.7-0.9 were determined. It has been found that the rate coefficients of the OH + alkyl formates reactions depend significantly on the alkyl group. Experimental and theoretical considerations have been made to compare the reactivity of the formate and formyl groups in OH radical reactions. Ab initio calculations were used to explain the 2 orders of magnitude greater reactivity of the formyl group. Determination of enthalpies of formation of free radicals: Bromination reactions were studied using the "kinetic equilibrium" method. The "third-law" procedure was applied to derive the enthalpies of formation for free radicals CH2OH (-17.62 - 2.0 kJ mol-1), CH3C(O)CH2 (-28 kJ mol-1), and CHClBr (140 - 4 kJ mol-1). Development of thermodynamic database for free radicals: Compilation and critical evaluation of literature data (and own computational results) were used to build up the database. Datasheets for 11 free radicals were published so far
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