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[Bis(pyridine)iodine(I)]+ complexes offer controlled access to halonium ions under mild conditions. The reactivity of such stabilized halonium ions is primarily determined by their three‐center, four‐electron [N−I−N]+ halogen bond. We studied the importance of chelation, strain, steric hindrance and electrostatic interaction for the structure and reactivity of halogen bonded halonium ions by acquiring their 15N NMR coordination shifts and measuring their iodenium release rates, and interpreted the data with the support of DFT computations. A bidentate ligand stabilizes the [N−I−N]+ halogen bond, decreasing the halenium transfer rate. Strain weakens the bond and accordingly increases the release rate. Remote modifications in the backbone do not influence the stability as long as the effect is entirely steric. Incorporating an electron‐rich moiety close by the [N−I−N]+ motif increases the iodenium release rate. The analysis of the iodine(I) transfer mechanism highlights the impact of secondary interactions, and may provide a handle on the induction of stereoselectivity in electrophilic halogenations., Halogen bond‐stabilized halonium ions are mild halenium transfer agents. The dependence of their reactivity on chelation, strain, steric hindrance and electrostatic interaction has been evaluated using NMR, DFT and kinetics experiments. The mechanistic analysis of the transfer is expected to provide a handle in the induction of stereoselectivity in electrophilic halogenations.

We demonstrate herein the capacity of simple carboxylate salts - tetrametylammonium and tetramethylguanidinium pivalate - to act as catalysts in the isomerization of β,γ-unsaturated thioesters to α,β-unsaturated thioesters. The carboxylate catalysts gave reaction rates comparable to those obtained with DBU, but with fewer side reactions. The reaction exhibits a normal secondary kinetic isotope effect (k

The joint neutron/X-ray crystallographic structure of perdeuterated Aspergillus flavus urate oxidase in complex with the inhibitor 8-azaxanthine and a catalytic water bound in the peroxo hole is presented together with an integrated analysis using biomolecular simulations., Cofactor-independent urate oxidase (UOX) is an ∼137 kDa tetrameric enzyme essential for uric acid (UA) catabolism in many organisms. UA is first oxidized by O2 to de­hydro­isourate (DHU) via a peroxo intermediate. DHU then undergoes hydration to 5-hy­droxy­isourate (5HIU). At different stages of the reaction both catalytic O2 and water occupy the ‘peroxo hole’ above the organic substrate. Here, high-resolution neutron/X-ray crystallographic analysis at room temperature has been integrated with molecular dynamics simulations to investigate the hydration step of the reaction. The joint neutron/X-ray structure of perdeuterated Aspergillus flavus UOX in complex with its 8-azaxanthine (8AZA) inhibitor shows that the catalytic water molecule (W1) is present in the peroxo hole as neutral H2O, oriented at 45° with respect to the ligand. It is stabilized by Thr57 and Asn254 on different UOX protomers as well as by an O—H⋯π interaction with 8AZA. The active site Lys10–Thr57 dyad features a charged Lys10–NH3 + side chain engaged in a strong hydrogen bond with Thr57OG1, while the Thr57OG1–HG1 bond is rotationally dynamic and oriented toward the π system of the ligand, on average. Our analysis offers support for a mechanism in which W1 performs a nucleophilic attack on DHUC5 with Thr57HG1 central to a Lys10-assisted proton-relay system. Room-temperature crystallography and simulations also reveal conformational heterogeneity for Asn254 that modulates W1 stability in the peroxo hole. This is proposed to be an active mechanism to facilitate W1/O2 exchange during catalysis.

The determination of drug residence times, which define the time an inhibitor is in complex with its target, is a fundamental part of the drug discovery process. Synthesis and experimental measurements of kinetic rate constants are, however, expensive and time consuming. In this work, we aimed to obtain drug residence times computationally. Furthermore, we propose a novel algorithm to identify molecular design objectives based on ligand unbinding kinetics. We designed an enhanced sampling technique to accurately predict the free-energy profiles of the ligand unbinding process, focusing on the free-energy barrier for unbinding. Our method first identifies unbinding paths determining a corresponding set of internal coordinates (ICs) that form contacts between the protein and the ligand; it then iteratively updates these interactions during a series of biased molecular dynamics (MD) simulations to reveal the ICs that are important for the whole of the unbinding process. Subsequently, we performed finite-temperature string simulations to obtain the free-energy barrier for unbinding using the set of ICs as a complex reaction coordinate. Importantly, we also aimed to enable the further design of drugs focusing on improved residence times. To this end, we developed a supervised machine learning (ML) approach with inputs from unbiased "downhill"trajectories initiated near the transition state (TS) ensemble of the string unbinding path. We demonstrate that our ML method can identify key ligand-protein interactions driving the system through the TS. Some of the most important drugs for cancer treatment are kinase inhibitors. One of these kinase targets is cyclin-dependent kinase 2 (CDK2), an appealing target for anticancer drug development. Here, we tested our method using two different CDK2 inhibitors for the potential further development of these compounds. We compared the free-energy barriers obtained from our calculations with those observed in available experimental data. We highlighted important interactions at the distal ends of the ligands that can be targeted for improved residence times. Our method provides a new tool to determine unbinding rates and to identify key structural features of the inhibitors that can be used as starting points for novel design strategies in drug discovery.

Metal/organic-molecule interactions underpin many key chemistries but occur on sub-nm scales where nanoscale visualisation techniques tend to average over heterogeneous distributions. Single molecule imaging techniques at the atomic scale have found it challenging to track chemical behaviour under ambient conditions. Surface-enhanced Raman spectroscopy can optically monitor the vibrations of single molecules but understanding is limited by the complexity of spectra and mismatch between theory and experiment. We demonstrate that spectra from an optically generated metallic adatom near a molecule of interest can be inverted into dynamic sub-Å metal-molecule interactions using a comprehensive model, revealing anomalous diffusion of a single atom. Transient metal-organic coordination bonds chemically perturb molecular functional groups > 10 bonds away. With continuous improvements in computational methods for modelling large and complex molecular systems, this technique will become increasingly applicable to accurately tracking more complex chemistries., We acknowledge financial support from EPSRC grant EP/G060649/1, EP/L027151/1, EP/G037221/1, EP/R013012/1, EPSRC NanoDTC, and EU grant THOR 829067 and ERC starting grant BioNet 757850. B.d.N. acknowledges support from the Leverhulme Trust and Isaac Newton Trust. We acknowledge use of the Rosalind computing facility at King’s College London. We are grateful to the UK Materials and Molecular Modelling Hub for computational resources, which is partially funded by EPSRC 397 (EP/P020194/1).

The first halonium‐ion‐based helices were designed and synthesized using oligo‐aryl/pyridylene‐ethynylene backbones that fold around reactive iodonium ions. Halogen bonding interactions stabilize the iodonium ions within the helices. Remarkably, the distance between two iodonium ions within a helix is shorter than the sum of their van der Waals radii. The helical conformations were characterized by X‐ray crystallography in the solid state, by NMR spectroscopy in solution and corroborated by DFT calculations. The helical complexes possess potential synthetic utility, as demonstrated by their ability to induce iodocyclization of 4‐penten‐1‐ol.

Understanding the interactions between molecules and metal surfaces is of widespread importance in electrochemistry, sensing, medical imaging/targeting, molecular electronics and spintronics. Although many techniques have characterized the molecule-metal transient bonds, conflicting conclusions arise from their buried location and heterogeneity, while single-molecule probes are scarce. Confinement of optical fields to picometre length-scales around adatoms (termed picocavities [1] , Fig. 1a ) has enabled tip-enhanced and surface-enhanced Raman spectroscopies (TERS and SERS, Fig. 1e ) of single-molecules. However how adatoms change with molecule-metal interactions, with light (both key ingredients in photocatalysis), and how they link to picocavity formation in metal nanogaps is not understood.

Immobilized first-row transition metal complexes are potential low-cost electrocatalysts for selective CO2 conversion in the production of renewable fuels. Mechanistic understanding of their function is vital for the development of next-generation catalysts, although the poor surface sensitivity of many techniques makes this challenging. Here, a nickel bis(terpyridine) complex is introduced as a CO2 reduction electrocatalyst in a unique electrode geometry, sandwiched by thiol-anchoring moieties between two gold surfaces. Gap-plasmon-assisted surface-enhanced Raman scattering spectroscopy coupled with density functional theory calculations reveals that the nature of the anchoring group plays a pivotal role in the catalytic mechanism. Our in situ spectro-electrochemical measurement enables the detection of as few as eight molecules undergoing redox transformations in individual plasmonic hotspots, together with the calibration of electrical fields via vibrational Stark effects. This advance allows rapid exploration of non-resonant redox reactions at the few-molecule level and provides scope for future mechanistic studies of single molecules. Tracking immobilized molecular complexes under in situ conditions is vital for the development of next-generation catalysts, although the poor surface sensitivity of many techniques makes this challenging. Now, the role of the anchoring group in a nickel bis(terpyridine) complex has been elucidated by in situ gap-plasmon-assisted SERS coupled with DFT calculations.

The reactivity of halonium ions is conveniently modulated by three-center, four-electron halogen bonds. Such stabilized halonium complexes are valuable reagents for oxidations and halofunctionalization reactions. We report the first example of the stabilization of a halenium ion in a three-center, four-electron halogen bond with two oxygen ligands. The influence of electron density and solvent on the stability of the complexes is assessed. O–I–O halogen bond complexes are applicable as synthetic reagents and as supramolecular synthons.

Carboxylic acids and their corresponding carboxylate anions are generally utilized as Brønsted acids/bases and oxygen nucleophiles in organic synthesis. However, a few asymmetric reactions have used carboxylic acids as electrophiles. Although chiral thioureas bearing both arylboronic acid and tertiary amine were found to promote the aza-Michael addition of BnONH2 to α, β-unsaturated carboxylic acids with moderate to good enantioselectivities, the reaction mechanism remains to be clarified. Detailed investigation of the reaction using spectroscopic analysis and kinetic studies identified tetrahedral borate complexes, comprising two carboxylate anions, as reaction intermediates. We realized a dramatic improvement in product enantioselectivity with the addition of 1 equiv of benzoic acid. In this aza-Michael reaction, the boronic acid not only activates the carboxylate ligand as a Lewis acid, together with the thiourea NH-protons, but also functions as a Brønsted base through a benzoyloxy anion to activate the nucleophile. Moreover, molecular sieves were found to play an important role in generating the ternary borate complexes, which were crucial for obtaining high enantioselectivity as demonstrated by DFT calculations. We also designed a new thiourea catalyst for the intramolecular oxa-Michael addition to suppress another catalytic pathway via a binary borate complex using steric hindrance between the catalyst and substrate. Finally, to demonstrate the synthetic versatility of both hetero-Michael additions, we used them to accomplish the asymmetric synthesis of key intermediates in pharmaceutically important molecules, including sitagliptin and α-tocopherol.

Presence of the antidepressant fluoxetine in different water bodies has raised significant concerns due to its detrimental effects on non-targeted organisms, especially on fish. When seeking for an appropriate technology able to remove fluoxetine residue from a complex water matrix, special attention needs to be paid to the elimination of the neurophysiological activity that eventually lies behind the noxious effects of the parent compound. Our aim was to probe the applicability of advanced oxidation techniques for this purpose using in situ generated free radical system based on OH-initiated peroxyl radical-mediated processes. By performing product analysis experiments along with quantum chemical calculations, the most probable reaction paths were analyzed including aromatic hydroxylation, defluorination, O-dealkylation and C-dealkylation. The candidates for neurophysiological activity were further investigated by molecular docking. The hydroxylated derivatives are well accommodated in the binding pocket of the corresponding protein, suggesting that these compounds may retain the activity of the parent compound. From a worst-case perspective, we suggest that prolonged treatment needs to be applied to further transform hydroxylated derivatives.

• Combined computational and experimental work to probe Lewis acidity of some boranes to be used in FLP hydrogenation.

More than 2600 coprolites produced by vertebrates have been found in the fluvial lacustrine beds of the Upper Cretaceous (Santonian) Csehbanya Formation, Iharkut, western Hungary. In this study the mineral components, embedded dietary residues of these coprolites were examined and their ecological significance are discussed. The coprolite assemblage, containing mostly small-sized (length between 0.8 and 8.6 cm) specimens, can be ordered into seven different morphotypes, among which the spiral ones might have been produced by fish with spiral intestinal valves. The surface of the coprolites is mostly smooth and desiccation cracks were observed in only one case, suggesting that most of these coprolites were buried in-situ without long-term subaerial exposure. The fine-grained matrix of coprolites contains small holes, partially digested plant and animal residues but no sedimentary particles. CT-scanning was an effective method for revealing embedded dietary residues despite that the coprolites contain a large amount of pyrite. The coprolites contain cuticle remains, coalified seeds, pollen grains and diatoms. Animal residues may be the evidence of predation: mollusk shell and bone fragments, ganoid scales of Lepisosteiformes fish were frequent and one Pycnodontiformes fish tooth was found as well. It is not possible to ascertain the real producer of the coprolites, but, according to these remains, the Lepisosteiformes and Pycnodontiformes fish were included in the producer's prey. Not only the bone- but also the plant-bearing coprolites are highly phosphatic with mineral apatite in their matrix. However, the embedding fluvial sediment has significantly different chemical composition. The high phosphatic content of coprolites and the apatite might be derived from the carnivorous diet. Plant remains in the phosphatic coprolites may imply an omnivore producer or were the result of their incidental ingestion. Rapid burial and the mineral content of the animal nutriment might have been the responsible factors for the good preservation of the excrements.

Aromatic ring hydroxylation reactions occurring during radiolysis of aqueous solutions are studied on the example of phenylurea herbicides by Density Functional Theory calculations. The effect of the aqueous media is taken into account by using the Solvation Model Based on Density model. Hydroxyl radical adds to the ring because the activation free energies (0.4–47.2 kJ mol−1) are low and also the Gibbs free energies have high negative values ((−27.4) to (−5.9) kJ mol−1). According to the calculations in most of cases the ortho- and para-addition is preferred in agreement with the experimental results. In these reactions hydroxycyclohexadienyl type radicals form. In a second type reaction, when loss of chlorine atom takes place, OH/Cl substitution occurs without cyclohexadienyl type intermediate.

In this study, we have developed a highly enantioselective organocatalytic route to the (1

Four distinct folding patterns were identified in two foldamer-type urea-thiourea catalysts bearing a basic dimethylamino unit by a combination of X-ray crystallography, solution NMR studies, and computational studies (DFT). These patterns are characterized by different intramolecular hydrogen bonding schemes that arise largely from different thiourea conformers. The free base forms of the catalysts are characterized by folds where the intramolecular hydrogen bonds between the urea and the thiourea units remain intact. In contrast, the catalytically relevant salt forms of the catalyst, where the catalyst forms an ion pair with the substrate or substrate analogues, appear in two entirely different folding patterns. With larger anions that mimic the dialkyl malonate substrates, the catalysts maintain its native fold both in the solid state and in solution, but with smaller halide anions (fluoride, chloride and bromide), the catalysts fold around the halide anion (anion receptor fold) and the intramolecular hydrogen bonds are disrupted. Titration of catalyst hexafluoroacetylacetonate salt with tetra-n-butylammonium chloride results in dynamic refolding of the catalyst from the native fold to the anion receptor fold. peerReviewed

A full account of the •OH-induced free radical chemistry of an arylalkylamine is given taking all the possible reaction pathways quantitatively into consideration. Such knowledge is indispensable w...

The decomposition of monuron was investigated in dilute aqueous solutions using pulse radiolysis and γ-radiolysis in order to identify the intermediates and final products. The main reaction takes place between monuron and the hydroxyl radicals yielding hydroxycyclohexadienyl type radicals with a second order rate constant of (7.4±0.2)×10 9 mol −1 dm 3 s −1 . In ∙ OH reactions, the aminyl and phenoxyl radicals may also form. Dechlorination was observed in both hydroxyl radical and hydrated electron reactions. The ∙ OH induced dechlorination reactions are suggested to occur through OH substitution or phenoxyl radical formation. The rate of oxidation is very high in the presence of dissolved oxygen. Some of the results are also supported by quantum chemical calculations.

A range of amines catalyse the oxidative addition (OA) of H2 to [(Me3Si)2CH]2Sn (1), forming [(Me3Si)2CH]2SnH2 (2). Experimental and computational studies point to ‘frustrated Lewis pair’ mechanisms in which 1 acts as a Lewis acid and involve unusual late transition states; this is supported by the observation of a kinetic isotope effect Image ID:c8sc03110j-t1.gif for Et3N. When DBU is used the energetics of H2 activation are altered, allowing an equilibrium between 1, 2 and adduct [1·DBU] to be established, thus demonstrating reversible oxidative addition/reductive elimination (RE) of H2 at a single main group centre.

Nowadays X-ray computed tomography (CT) imaging is being applied in the field of structural engineering. Scanning a concrete specimen by using X-ray tomography provides an insight into the ...

A ‘frustrated Lewis pair’-type mechanism allows the first observation of reversible H2 addition to a single-site main-group complex., A range of amines catalyse the oxidative addition (OA) of H2 to [(Me3Si)2CH]2Sn (1), forming [(Me3Si)2CH]2SnH2 (2). Experimental and computational studies point to ‘frustrated Lewis pair’ mechanisms in which 1 acts as a Lewis acid and involve unusual late transition states; this is supported by the observation of a kinetic isotope effect for Et3N. When DBU is used the energetics of H2 activation are altered, allowing an equilibrium between 1, 2 and adduct [1·DBU] to be established, thus demonstrating reversible oxidative addition/reductive elimination (RE) of H2 at a single main group centre.

Unstable N-heterocyclic carbenes can be masked and stabilized as pseudo-cross-conjugated hetarenium-carboxylates which decarboxylate on warming. This study deals with the decarboxylation of carboxylates of mesoionic compounds to generate anionic N-heterocyclic carbenes. Lithium sydnone-4-carboxylates were therefore prepared via 4-bromosydnones by halogen-lithium exchange with nBuLi and subsequent treatment with carbon dioxide. Protonation gave the corresponding sydnone-4-carboxylic acids. Thermogravimetric measurements in addition to temperature dependent IR spectroscopy proved the decarboxylation of lithium sydnone-4-carboxylates and formation of the corresponding sydnone anions which can be represented as anionic N-heterocyclic carbenes. In DMSO-d6 solution, water favors the decarboxylation. Calculations have been performed to elucidate the mechanism of the decarboxylation in the absence and presence of water. (C) 2018 Elsevier Ltd. All rights reserved.

In this paper, we report on the development of a bench-stable borane for frustrated Lewis pair catalyzed reduction of aldehydes, ketones, and enones. The deliberate fine-tuning of structural and electronic parameters of Lewis acid component and the choice of Lewis base provided for the first time, a moisture-tolerant FLP catalyst. Related NMR and DFT studies underpinned the unique behavior of this FLP catalyst and gave insight into the catalytic activity of the resulting FLP catalyst.

Kutatásunk során a belvíz talajszerkezetre gyakorolt hatását modelleztük háromszor ismételt nedvesítési–száradási ciklussal (WDC) négy darab, közel 10 ezer cm3 térfogatú, bolygatatlan talajmintán. A talajszerkezet változását vizsgáltuk komputertomográffal (CT), annak érdekében, hogy 1) a minták belso szerkezeti viszonyait láthatóvá tegyük, 2) a mintavételezéssel járó, zavaró falhatást kiküszöbölhessük és 3) a nedvesítési–száradási ciklusok után összehasonlító elemzést végezhessünk. A három nedvesedési-száradási ciklusból álló kísérlet során az eredendően talajhibától mentes, jó vízgazdálkodású, jó minoségű talajmintákat 880 × 880 µm2 pixel felbontásban felvételeztük komputertomográffal. Meghatároztuk a vizsgálat szempontjából reprezentatív elemi térfogatot, majd a talajoszlopokat e térfogati elemekre osztva elemeztük tovább. A CT-vel mért, sűrűséget jelző Hounsfield-egységeket átszámoltuk száraz térfogattömeg értékekre. A kísérlet eredményeként a bolygatatlan minták kismértékű térfogattömeg növekedését, valamint a nagyobb méretű pórusok arányának csökkenését figyeltük meg. Ezáltal igazoltuk, hogy talajművelési beavatkozás nélkül, a belvíz okozta tartós vízborítás alatt álló talajok szerkezeti degradációja a későbbiekben tovább növelheti a területen a belvízkockázatot.

Feeding in thyreophoran dinosaurs is poorly understood. Although the group existed for over 130 million years, only the Early Jurassic basal thyreophoran Scelidosaurus harrisonii and the Late Cretaceous ankylosaurid Euoplocephalus tutus have been studied from this perspective in detail. In contrast to the earlier, conservative hypothesis of a simple "orthal pulping" feeding mode with no or limited tooth-tooth contact, recent studies have demonstrated precise dental occlusion with differing jaw mechanisms in these two species. Here, we describe the first detailed study of feeding related characters in a nodosaurid ankylosaur, Hungarosaurus tormai, from the Late Cretaceous of Hungary. Dental wear patterns comprising small, apical, and low-angled facets on the maxillary and steep, extended, and bowl-like facets on the dentary teeth reveal sophisticated tooth-tooth contact in this basal nodosaurid. The presence of two different scratch generations (vertical and low-angled) on the dentary teeth unambiguously demonstrate a multiphasic powerstroke, which is further supported by the morphology of the quadrate-articular and mandibular symphyseal joints and by the architecture of the reconstructed jaw adductors. Chewing started with an initial slicing phase associated with orthal movement that was followed by a retractive powerstroke with significant occlusal contact. Because of the curved tooth rows, these movements were probably facilitated by some mediolateral translation and/or axial rotation of the mandibles to produce precise shearing along the whole tooth row. These results demonstrate that complex jaw mechanisms and dental occlusion were more widespread among thyreophorans than thought previously and that palinal movement was present in at least two ankylosaurian lineages.

A full account of the

Catalysts containing urea, thiourea and tertiary amine groups fold into a three-dimensional organized structure in solution both in the absence as well as in the presence of substrates or substrate analogues, as indicated by solution NMR and computational studies. These foldamer catalysts promote Mannich reactions with both aliphatic and aromatic imines and malonate esters. Hammett plot and secondary kinetic isotope effects provide evidence for the C-C bond forming event as the turnoverlimiting step of the Mannich reaction. Computational studies suggest two viable pathways for the C-C bond formation step, differing in the activation modes of the malonate and imine substrates. The results show that the foldamer catalysts may promote C-C bond formation with an aliphatic substrate bearing a cyclohexyl group by enhanced binding of the substrates by dispersion interactions, but these interactions are largely absent with a simpler catalyst. Additional control experiments demonstrate the ability of simple thiourea catalysts to promote competing side reactions with aliphatic substrates, such as reversible covalent binding of the thiourea sulfur to the imine which deactivates the catalyst, and imine-to-enamine isomerization reactions. In foldamer catalysts, the nucleophilicity of sulfur is reduced, which prevents catalyst deactivation. The results indicate that the improved catalytic performance of foldamer catalysts in Mannich reactions may not be due to cooperative effects of intramolecular hydrogen bonds, but simply due to the presence of the folded structure that provides an active site pocket, accommodating the substrate and at the same time impeding undesirable side reactions. peerReviewed

The enantioselectivity of amine-catalyzed reactions of aldehydes with electrophiles is often explained by simple steric arguments emphasizing the role of the bulky group of the catalyst that prevents the approach of the electrophile from the more hindered side. This standard steric shielding model has recently been challenged by the discovery of stable downstream intermediates, which appear to be involved in the rate-determining step of the catalytic cycle. The alternative model, referred to as Curtin-Hammett scenario of stereocontrol, assumes that the enantioselectivity is related to the stability and reactivity of downstream intermediates. In our present computational study, we examine the two key processes of the catalytic Michael reaction between propanal and β-nitrostyrene that are relevant to the proposed stereoselectivity models, namely the C-C bond formation and the protonation steps. The free energy profiles obtained for the pathways leading to the enantiomeric products suggest that the rate- and stereo-determining steps are not identical as implied by the previous models. The stereoselectivity can be primarily controlled by C-C bond formation even though the reaction rate is dictated by the protonation step. This kinetic scheme is consistent with all observations of experimental mechanistic studies including those of mass spectrometric back reaction screening experiments, which reveal a mismatch between the stereoselectivity of the back and the forward reactions. peerReviewed

The parahydrogen-induced polarization (PHIP) phenomenon, observed when parahydrogen is used in H-2 addition processes, provides a means for substantial NMR signal enhancements and mechanistic studies of chemical reactions. Commonly, noble metal complexes are used for parahydrogen activation, whereas metal-free activation is rare. Herein, we report a series of unimolecular metal-free frustrated Lewis pairs based on an ansa-aminoborane (AAB) moiety in the context of PHIP. These molecules, which have a "molecular tweezers'' structure, differ in their substituents at the boryl site (-H, -Ph, -o-iPr-Ph, and -Mes). PHIP effects were observed for all the AABs after exposing their solutions to parahydrogen in a wide temperature range, and experimental measurements of their kinetic and thermodynamic parameters were performed. A theoretical analysis of their nuclear spin polarization effects is presented, and the roles of chemical exchange, chemical equilibrium and spin dynamics are discussed in terms of the key dimensionless parameters. The analysis allowed us to formulate the prerequisites for achieving strong polarization effects with AAB molecules, which can be applied for further design of efficient metal-free tweezers-like molecules for PHIP. Mechanistic (chemical and physical) aspects of the observed effects are discussed in detail. In addition, we performed quantum chemical calculations, which confirmed that the J-coupling between the parahydrogen-originated protons in AAB-H-2 molecules is mediated through dihydrogen bonding.

Peridotite xenoliths showing unusual tabular equigranular textures (addressed as flattened tabular equigranular) were found in Neogene alkali basalts from the Bakony-Balaton Highland Volcanic Field (Western Hungary), Carpathian-Pannonian Region. The olivines have a characteristic crystallographic preferred orientation (CPO) with [0 1 0]-axes perpendicular to the foliation and the [1 0 0]- and [0 0 1]-axes forming a continuous girdle in the foliation plane. Contrarily, the CPO pattern of orthopyroxene is much more scattered, although a single maximum can be observed in [0 0 1] axes subparallel to the plane of foliation. In case of olivine, the activation of (0 1 0)[1 0 0] and also probably (0 1 0)[0 0 1] is suggested. The deformation micro-mechanisms of orthopyroxenes are suggested to be a combination of intracrystalline glide on the (1 0 0)[0 0 1] system and some kind of other mechanism resulting in quite scattered patterns. We suggest that the unusual orientation patterns of olivines and orthopyroxenes are the result of the complex tectonic evolution of the region. The flattened tabular equigranular xenoliths represent a structural domain within the subcontinental lithospheric mantle beneath the volcanic field with particular seismic characteristics. The occurrence of flattened domains in the upper mantle may considerably influence the percolation and residence time of the mantle melts and fluids, which could promote or prevent melt/wall-rock interaction.

We examined the Csaloka Spring, which has the highest radon concentration in the Sopron Mountains (West Hungary) (, yearly average of 227 ± 10 Bq L(-1)). The main rock types here are gneiss and micaschist, formed from metamorphism of former granitic and clastic sedimentary rocks respectively. The aim of the study was to find a likely source of the high radon concentration in water. During two periods (2007-2008 and 2012-2013) water samples were taken from the Csaloka Spring to measure its radon concentration (from 153 ± 9 Bq L(-1) to 291 ± 15 Bq L(-1)). Soil and rock samples were taken within a 10-m radius of the spring from debrish and from a deformed gneiss outcrop 500 m away from the spring. The radium activity concentration of the samples (between 24.3 ± 2.9 Bq kg(-1) and 145 ± 6.0 Bq kg(-1)) was measured by gamma-spectroscopy, and the specific radon exhalation was determined using radon-chamber measurements (between 1.32 ± 0.5 Bq kg(-1) and 37.1 ± 2.2 Bq kg(-1)). Based on these results a model calculation was used to determine the maximum potential radon concentration, which the soil or the rock may provide into the water. We showed that the maximum potential radon concentration of these mylonitic gneissic rocks (cpot = 2020 Bq L(-1)) is about eight times higher than the measured radon concentration in the water. However the maximum potential radon concentration for soils are significantly lower (41.3 Bq L(-1)) Based on measurements of radon exhalation and porosity of rock and soil samples we concluded that the source material can be the gneiss rock around the spring rather than the soil there. We determined the average radon concentration and the time dependence of the radon concentration over these years in the spring water. We obtained a strong negative correlation (-0.94 in period of 2007-2008 and -0.91 in 2012-2013) between precipitation and radon concentration.

This paper summarizes the benefits of non-destructive core measurements by medical Computer Tomograph (CT) in integrated 3D reservoir characterization. A direct relationship exists between CT measurements and petrography, conventional petrophysical analysis and well logs. Based on CT measurements the internal structure of core samples, and the geometry of framework constituents, porosity type and pore size distribution, as well as fracturing, can be described. There is a close connection between distribution of the Hounsfield Unit of CT measurements and pore size distribution detected by conventional petrophysical analysis. Calculation of effective porosity from petroleum saturation experiments provides a new way to determine the porosity of the whole core sample. Beside the description of reservoir parameters, the results of CT measurements can be extended over the surrounding area of the well. By matching the cylinder maps of CT to FMI images and other well logs the original position of the core sample...

A szerzok laboratóriumi talajérleléses kísérletet állítottak be meszes Duna öntéstalajon különbözo elemi kén dózisok (0,1 g; 1,0 g; 2,5 g; 5,0 g; illetve 10 g/tenyészedény, azaz 50, 500, 1250, 2500 és 5000 kg ha-1) talajbeli oxidációjának vizsgálata céljából mutrágyázatlan, illetve NPK-mutrágyázott körülmények között. A 84 napos inkubációs periódus elteltével a talajok pH(H2O),pH(KCl) értékeit, valamint a talajokban mérheto, vízoldható szulfátion-koncentrációt elemezték. Az eredményeket varianciaanalízis és regressziószámítás segítségével értékelték. Az elvégzett vizsgálatok alapján megállapították, hogy a mutrágyázatlan talajok különbözo elemi kén adagok hatására kialakult pH-értékei szignifikáns különbséget nem mutattak, míg a mutrágyázott kezelések esetén az emelkedo kéndózisok hatására bekövetkezo pH-csökkenés 0,1 %-os szignifikancia szinten általánosnak bizonyult. A talajok felveheto szulfátion-koncentrációja vélhetoen a kezelések, valamint a talajok mikrobiális tevékenységének hatására minden esetben nott. Az elemi kén adagok, valamint a talajok mért szulfátion-koncentrációinak 0,1 %-os szignifikancia szinten érvényesülo összefüggései azonban a talaj pH-értékeinek alakulásával bizonyítható kapcsolatot nem mutattak. A látszólagos ellentmondás hátterében számos biológiai, fizikai és kémiai tényezo állhat, melyek meghatározása a kapott összefüggések tisztázása szempontjából további vizsgálatok szükségességét veti fel.