A talaj tápanyag ellátottságának és a szimbionta partnerek kompatibilitásának szerepe néhány mezőgazdasági haszonnövény mikorrhiza függésében = Studying the nutrient supply of soil and compatibility of symbiotic partners in mycorrhiza dependency at several agricultural crops

Meghatároztuk a talaj nitrogén ellátásának, a növények mikorrhiza függésének és az AM gombák gyökérkolonizációjának viszonyát, a szimbiózis időbeni alakulását a nitrogén és foszfor ellátás együttes hatásától függően. Megállapítottuk, hogy a szimbiotikus AM gombák apresszóriumainak számának alakulása egy fontos indikátora lehet nemcsak a fertőzőképességének, a talaj tápanyag ellátottságának, de a szimbiózis hatékonyságára is utal. Az AM gombaoltás hatékonyságát a növényfaj, a tesztnövény vegetációs állapota és nitrogén ellátottsága egyaránt befolyásolta. A fiatal növények nitrogén felvétele és foszforfelvétele között negatív korrelációt találtunk. A tesztnövényekben "optimális" tápanyag ellátottság mellett, amely esetünkben az 100 mg N kg-1 talaj (300 kg N ha év-1 ) dózis volt csökken a gombák kolonizációja. A kolonizáció csökkenése a gombának juttatott fotoszintetikus asszimilátumok mennyiségének csökkentésével magyarázható. A nitrogénnel bőségesen ellátott (150 mg N kg-1 talaj; 450 kg N ha év-1 ) növények foszforhiányban szenvednek, amely a mikorrhiza gombák kolonizációjának növelésével enyhíthető. Hazai AM gombafajok "egyspórás" kultúrákat hoztunk létre. Módszert dolgoztunk ki az oltóanyagok minősítésére. Hazai és külföldi eredetű Glomus sp. törzsek között, infektivitási és effektivitási tulajdonságaik alapján intra- és interspecifikus funkcionális diverzitást mutattunk ki. A hazai talajokból izolált törzsek, különös tekintettel egy Glomus mosseae törzs gombái a hazai talajhoz ill. körülményekhez jobban adaptálódtak és hatékonyabb növény-gomba szimbiózist alakítottak ki. | Data were obtained about the relation of soil N supply the mycorrhiza dependency of plants and root colonization of AM fungi furthermore the timing of symbiosis formation. The formation of mycorrhiza is influenced by available P concentration in soil, by the developmental stage of the host and even by the relative amount of N. The number of AM fungal entry points could be an important parameter for evaluation of both infectiveness and effectivenes of AMF. In young plants the P content of shoots showed negative correlation to N uptake. When host are not nutrient limited the AMF were initially C-limited and the colonization decreased. In our experiment the lowest Gl. mosseae colonization was detected at 100 mg N kg-1 (300 kg N ha year-1 ) level. We suggest that at the highest N fertilization (150 mg kg –1; 450 kg N ha year-1 ) the host should become P- or other macronutrient-limited and the AMF colonization was altered to improve the nutrient transport of hyphae from the soil to the plant. The symbiosis between host plant and AM fungi dinamically changes according to the soil nutrient supply and demands of developing plant. Monospore cultures of AM fungi were produced from Hungarian soil and a new methode was developed for quality control of AMF inocula. The inter- and intraspecific functional diversity of Glomus cultures were found in relation to plant response to AMF inoculation. The results confirmed the hypothesis that the indigenous AM fungi species or strains can be more efficient than other ones. These fungi are probably well adapted to the edaphic conditions of domestic soils

Huge negative differential conductance in Au-H2 molecular nanojunctions

Experimental results showing huge negative differential conductance in gold-hydrogen molecular nanojunctions are presented. The results are analyzed in terms of two-level system (TLS) models: it is shown that a simple TLS model cannot produce peaklike structures in the differential conductance curves, whereas an asymmetrically coupled TLS model gives perfect fit to the data. Our analysis implies that the excitation of a bound molecule to a large number of energetically similar loosely bound states is responsible for the peaklike structures. Recent experimental studies showing related features are discussed within the framework of our model.Comment: 9 pages, 8 figure

Elektron transzport nanokontaktusokban = Electron transport in nanojunctions

A pályázat keretében molekuláris nanokontaktusokat vizsgáltunk mechanikusan szabályozható törő kontaktus technika segítségével. Molekuláris kontaktusok alapvető jelenségeinek megértéséhez egy egyszerű modell rendszert választottunk: hidrogén molekulák kölcsönhatását vizsgáltuk atomi méretű kontaktusokkal. Megmutattuk, hogy a hidrogén erősen kölcsönhat atomi aranyláncokkal. A hidrogén molekula akár be is épülhet az aranyláncba, sőt a hidrogén és a lánc közötti kötés olyan erős, hogy a hidrogénen keresztül további arany atomokat húzhatunk a láncba. Megmutattuk hogy arany?hidrogén kontaktusok feszültség?áram karakterisztikáiban gyakran jelentkezik óriási negatív differenciális vezetőképesség jelensége, ami egy kötött molekuláris állapot nagyszámú, hasonló energiájú gyengén kötött állapotba történő gerjesztésével magyarázható. Molekuláris nanokontaktusok transzmissziós valószínűségeinek meghatározásához egy szupravezető subgap struktúra mérésekre alkalmas mérőrendszert fejlesztettünk, amivel különböző szupravezető anyagok kölcsönhatását vizsgáltuk hidrogén molekulákkal. Nagystabilitású atomi méretű kontaktusok létrehozásában szerzett tapasztalatok alapján egy heterokontaktusok létrehozására alkalmas precíziós mérőrendszert fejlesztettünk. A rendszert sikeresen alkalmaztuk a spin-polarizáció lokális, nanométeres felbontású meghatározására szupravezető tű és mágneses minta közötti Andreev spektroszkópiai mérésekkel. | In the framework of this project molecular nanojunctions were investigated by the mechanically controllable break junction technique. The interaction of single-atom contacts and monoatomic chains with hydrogen molecules was chosen as a model system to study the fundamental properties of molecular nanojunctions. It was shown that hydrogen molecules strongly interact with atomic chains of gold. The hydrogen molecule can even be incorporated in the atomic-sized Au junction, and the experiments have demonstrated that this molecular hydrogen clamp is strong enough to pull out a chain of gold atoms from the electrodes. With the study of the I-V characteristics of gold-hydrogen junctions we have pointed out the appearance of huge negative differential conductance phenomenon, which was explained by the excitation of a strongly bound molecule to a large number of energetically similar loosely bound states. To study the transmission eigenvalues of molecular nanojunctions a setup for the measurement of superconducting subgap structures was developed, and the interaction of hydrogen molecules with various superconducting electrodes was studied. Based on the experience in creating high stability atomic-sized contacts a new, high precision sample holder was developed for the creation of heterocontacts. The setup was successfully applied to determine local, nano-scale spin polarization with Andreev spectroscopy measurements between a superconducting tip and a magnetic sample

Contributions to the economic analysis of even-aged silviculture: From simple models to complex analyses

In managed forests, the enormous complexity of an ecologic system meets a vast range of economic and other impact factors. Thus, to determine, analyze and understand economically optimal stand management is a task which has kept forest economists occupied for the past 200 years. The approach which has been followed since the days of Martin FAUSTMANN is the analysis of models which describe rather specific management scenarios using a set of clearly defined model assumptions. Unfortunately, the applicability of the findings to more general scenarios is limited. On the other side, the possibility of analyzing general management environments with single models is also limited by increasing complexity. Thus, a holistic understanding of optimal forest management is still missing. This statement also holds for the extensive field of optimal even-aged timber production, which essentially consists of only three main components, i.e., planting, thinning and final harvest. Therefore, this dissertation aims to make a contribution to further increase the general understanding of even-aged forest management. To achieve this goal three steps were taken. First, a qualitative analysis of a combined management plan including decisions on all three basic components is presented based on HALBRITTER and DEEGEN (2015). It provides a discussion of the direct and indirect dependencies between the decision variables of a rotation in a rather classical management environment. Second, three studies are presented which dissolve some of the classical model assumptions and extend the existing knowledge on even-aged forestry to relevant but more complex mangement questions. HALBRITTER (2015) includes natural regeneration and a shelter period in an even-aged system and explores the borders between the even- and uneven-aged management. Thereby, the influence of natural regeneration and the impact of several age classes were studied. HALBRITTER (2020) drops the assumption of stand homogeneity and investigates stand management under heterogeneous tree growth in which, for example, different social classes of trees are maintained. Lastly, HALBRITTER et al. (2020) extend the classical deterministic management environment in the direction of density-dependent hazard risk. This adds an additional aspect to the thinning and the rotation decision because, in this scenario, the probability of stand destruction can be controlled by thinning. As a third step, the studies above were embedded in a patchwork representing a conglomeration of models which are connected and validated by overlapping scopes. Using this approach, a wide range of different management scenarios can be covered by rather simple models. Thus, the complexity of the analysis decreases compared to single models with a more generally applicable framework and the problem of model complexity is mitigated. In addition, the inclusion of reference models with a particular focus on the management components stand establishment, thinning or rotation allows for a clear identification of the relationship between optimal stand management and the characteristics of a scenario. Applied to the qualitative analysis of the four studies above, the approach yields insights which contribute to a better understanding of even-aged forest management.:1. Introduction 2. The FAUSTMANN Framework 2.1 Model Definition 2.2 The FAUSTMANN Model 2.3 Assumptions 2.4 Basic Applications 2.4.1 The Rotation Model 2.4.2 The Thinning Model 2.4.3 The Planting Model 2.4.4 The Uneven-aged Model 3. Problem 4. Methodology 5. The Combined Model 5.1 Model 5.2 Optimal Management 5.3 Impact of Timber Price and Interest Rate 5.4 Discussion in Comparison to the Basic FAUSTMANN Applications 6. Extensions 6.1 Uneven-Aged Extension: The Double-Cohort Model 6.1.1 Even-Aged and Uneven-Aged Stands 6.1.2 Model 6.1.3 Optimal Management 6.1.4 Impact of Timber Price and Interest Rate 6.1.5 Discussion in Comparison to the Basic FAUSTMANN Applications 6.2 Heterogeneous Extension: The Heterogeneous Stand Model 6.2.1 Homogeneous and Heterogenous Stands 6.2.2 Model 6.2.3 Optimal Management 6.2.4 Impact of Timber Price and Interest Rate 6.2.5 Discussion in Comparison to the Basic FAUSTMANN Applications 6.3 Stochastic Extension: The Natural Risk Model 6.3.1 Deterministic and Stochastic Scenarios 6.3.2 Model 6.3.3 Optimal Management 6.3.4 Impact of Timber Price and Interest Rate 6.3.5 Discussion in Comparison to the Basic FAUSTMANN Applications 7. Conclusions 7.1 Optimal Management Strategy 7.1.1 Optimal Planting 7.1.2 Optimal Thinning 7.1.3 Optimal Rotation 7.2 The Patchwork Approach 7.2.1 Applicability of the Patchwork Approach 7.2.2 Limitations of the Patchwork Approach 7.2.3 Comparison to the Holistic Approach 8. Summar

Scanning Auger microscopy as applied to the analysis of highly textured YBaCu3Ox thin films

Scanning Auger electron spectroscopy and scanning electron microscopy have been used to investigate the local composition and structure of highly textured axis oriented YBaCuO films with thicknesses in the range 0.4–1 μm. The cuprate films were sputtered on MgO and sapphire (100)-oriented single-crystal substrates at room temperature followed by several anneal stages below or at 920°C in pure oxygen. The YBaCuO/sapphire sample was examined again after an additional 750°C air anneal for 24 h. By applying Auger line profiling on a freshly prepared cross-sectional surface of a thin cuprate film deposited on a sapphire substrate we have been able to show that barium aluminate segregation at grain boundaries is the main cause of the higher electrical resistance usually observed for cuprate films on Al2O3. The (drastic) reduction in Tc can be attributed to the substitution of aluminium in the cuprate at copper sites. Severe interdiffusion has been observed for the epitaxial c axis oriented YBaCu oxide films grown on an MgO substrate, which leads to a deterioration in the superconductivity. The main reason for reduced Tc and quality of cuprate films on MgO is the copper loss into the substrate, the depth of penetration of copper extending more than 400 nm below the YBaCuO---MgO interface. From our experimental results it is evident that Auger line profiling is an important tool in the analysis of high Tc superconducting thin films