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High-performance large-scale graph analytics are essential to timely analyze relationships in big datasets. Conventional processor architectures suffer from inefficient resource usage and bad scaling on those workloads. To enable efficient and scalable graph analysis, Intel developed the Programmable Integrated Unified Memory Architecture (PIUMA) as a part of the DARPA Hierarchical Identify Verify Exploit (HIVE) program. PIUMA consists of many multithreaded cores, fine-grained memory and network accesses, a globally shared address space, powerful offload engines, and a tightly integrated optical interconnection network. This article presents the PIUMA architecture and documents our experience in designing and building a prototype chip and its bring-up process. PIUMA silicon has successfully powered on demonstrating key aspects of the architecture, some of which will be incorporated into future Intel products.

This article draws on the prison experiences in Poland of the senior author to identify some of the major ingredients of the prison subculture in that country. The dominant inmate pattern of grypsing is described as is the physical environment of Polish prisons. This article also examines "prisonization" processes and the norms of the grypsing group. Some contrasts between American and Polish prisons are also noted.

Reaction of Ni(NCS)2with 4-(Boc-amino)pyridine in acetonitrile leads to the formation of a new coordination polymer with the composition Ni(NCS)2(4-(Boc-amino)pyridine)2·MeCN (1-MeCN). In the crystal structure the Ni(II) cations are linked by the anionic ligands into chains that are further connected into layers by intermolecular N–H···O hydrogen bonding. These layers are stacked and channels are formed, in which acetonitrile molecules are located. Solvent removal leads to the ansolvate 1, which shows microporosity as proven by sorption measurements. Single crystal X-ray investigations reveal that the solvent removal leads to a change in symmetry from primitive to C-centered, which is reversible and which proceeds via a topotactic reaction leaving the network intact. The magnetic properties of 1-MeCN and 1are governed by the ferromagnetic exchange between spins of Ni(II) forming chains. The susceptibility and specific heat for such a quantum Heisenberg chain of S= 1 spins with zero-field splitting are calculated using the DMRG method and compared with the experimental results.

Backward induction (BI) was one of the earliest methods developed for solving finite sequential games with perfect information. It proved to be especially useful in the context of Tom Schelling’s ideas of credible versus incredible threats. BI can be also extended to solve complex games that include an infinite number of actions or an infinite number of periods. However, some more complex empirical or experimental predictions remain dramatically at odds with theoretical predictions obtained by BI. The primary example of such a troublesome game is Centipede. The problems appear in other long games with sufficiently complex structure. BI also shares the problems of subgame perfect equilibrium and fails to eliminate certain unreasonable Nash equilibria.

Accurate predictions of net ecosystem productivity (NEPc) of forest ecosystems are essential for climate change decisions and requirements in the context of national forest growth and greenhouse gas inventories. However, drivers and underlying mechanisms determining NEPc(e.g., climate and nutrients) are not entirely understood yet, particularly when considering the influence of past periods. Here we explored the explanatory power of the compensation day (cDOY)—defined as the day of year when winter net carbon losses are compensated by spring assimilation—for NEPcin 26 forests in Europe, North America, and Australia, using different NEPcintegration methods. We found cDOY to be a particularly powerful predictor for NEPcof temperate evergreen needleleaf forests (R2= 0.58) and deciduous broadleaf forests (R2= 0.68). In general, the latest cDOY correlated with the lowest NEPc. The explanatory power of cDOY depended on the integration method for NEPc, forest type, and whether the site had a distinct winter net respiratory carbon loss or not. The integration methods starting in autumn led to better predictions of NEPcfrom cDOY then the classical calendar method starting 1 January. Limited explanatory power of cDOY for NEPcwas found for warmer sites with no distinct winter respiratory loss period. Our findings highlight the importance of the influence of winter processes and the delayed responses of previous seasons' climatic conditions on current year's NEPc. Such carry‐over effects may contain information from climatic conditions, carbon storage levels, and hydraulic traits of several years back in time. Compensation day (cDOY) is the day of year when net C losses during winter are compensated by net C uptake in springcDOY largely explains annual net ecosystem productivity NEPcof forests when the site has a distinct winter respiratory loss periodcDOY and its explanatory power depends on the integration method for annual NEPcand on the forest type

Cyclic AMP (cAMP) signaling is localized to multiple spatially distinct microdomains, but the role of cAMP microdomains in cancer cell biology is poorly understood. Here, we present a tunable genetic system that allows us to activate cAMP signaling in specific microdomains. We uncover a nuclear cAMP microdomain that activates a tumor-suppressive pathway in a broad range of cancers by inhibiting YAP, a key effector protein of the Hippo pathway, inside the nucleus. We show that nuclear cAMP induces a LATS-dependent pathway leading to phosphorylation of nuclear YAP solely at serine 397 and export of YAP from the nucleus with no change in YAP protein stability. Thus, nuclear cAMP inhibition of nuclear YAP is distinct from other known mechanisms of Hippo regulation. Pharmacologic targeting of specific cAMP microdomains remains an untapped therapeutic approach for cancer; thus, drugs directed at the nuclear cAMP microdomain may provide avenues for the treatment of cancer.

We study ground-state fidelity defined as the overlap between two ground states of the same quantum system obtained for slightly different values of the parameters of its Hamiltonian. We focus on the thermodynamic regime of the XY model and the neighborhood of its critical points. We describe extensively fidelity when it is dominated by the universal contribution reflecting the quantum criticality of the phase transition. We show that proximity to the multicritical point leads to anomalous scaling of fidelity. We also discuss fidelity in a regime characterized by pronounced oscillations resulting from the change in either the system size or the parameters of the Hamiltonian. Moreover, we show when fidelity is dominated by non-universal contributions, study fidelity in the extended Ising model, and illustrate how our results provide additional insight into dynamics of quantum phase transitions. Special attention is given to studies of fidelity from the momentum space perspective. All our main results are obtained analytically. They are in excellent agreement with numerics. [ABSTRACT FROM AUTHOR]

To facilitate discovery of compounds modulating sphingosine-1-phosphate (S1P) signaling, the authors used high-throughput mass spectrometry technology to measure S1P formation in human whole blood. Since blood contains endogenous sphingosine (SPH) and S1P, mass spectrometry was chosen to detect the conversion of an exogenously added 17-carbon-long variant of sphingosine, C17SPH, into C17S1P. The authors developed procedures to achieve homogeneous mixing of whole blood in 384-well plates and for a method requiring minimal manipulations to extract S1P from blood in 96- and 384-well plates prior to analyses using the RapidFire® mass spectrometry system.

The synthesis and spectroscopic characterization of [Cp*2Mo2P2Se3] (1; Cp* = C5Me5) and its use as a molecular building block in the formation of copper(I) halide polymers is described. The reaction of 1in CH2Cl2with 2 equiv. of CuBr and CuI in CH3CN under diffusion conditions gave [(Cp*2Mo2P2Se3)2(CuBr)2] (2) and [(Cp*2Mo2P2Se3)(CuX)3(CH3CN)]n(X = I; 3/4), respectively. The structure of 2is distinguished by a central Cu2Br2ring coordinated on each side by a tripledecker complex through one of its P atoms. A 2D network is formed by weak interactions between Se atoms of neighboring molecules. Compound [(Cp*2Mo2P2Se3)(CuI)3(CH3CN)]nexists in two isomeric forms 3and 4. The crystal structure of 3can be described as a two‐dimensional polymer that is formed by ribbons containing looped chains of three Cu2I2rings and attached [Cp*2Mo2P2Se3] molecules. The structure of 4contains a ribbon in which tripledecker molecules are linked through their P atoms to (CuI)6clusters. The ribbons are connected by weak Se···Se interactions. The reaction of a mixture of 1and P4Se3with CuI gave [(Cp*2Mo2P2Se3)(P4Se3)(CuI)2]n. The crystal structure analysis of 5reveals a new type of organometallic–inorganic framework in which 1and P4Se3are linked by Cu2I2rings.

ABSTRACTBy using a detergent-washed membrane preparation, the interaction of the fungal natural product inhibitor aureobasidin A (AbA) with inositol phosphorylceramide synthase (IPC synthase) was studied by kinetic analysis of wild-type and mutant enzyme-catalyzed reactions. AbA inhibited the wild-type enzyme from both Candida albicansand Saccharomyces cerevisiaein an irreversible, time-dependent manner, with apparent Kivalues of 183 and 234 pM, respectively. Three synthetic chemistry-derived AbA derivatives, PHA-533179, PHA-556655, and PHA-556656, had affinities 4 to 5 orders of magnitude lower and were reversible inhibitors that competed with the donor substrate phosphatidylinositol (PI). AbA was a reversible, apparently noncompetitive inhibitor, with a Kiof 1.4 μM, of the IPC synthase from an AbA-resistant S. cerevisiaemutant. The Kmvalues for both substrates (ceramide and PI) were similar when they interacted with the mutant and the wild-type enzymes. By contrast, the Vmaxfor the mutant enzyme was less than 10% of that for the wild-type enzyme. A comparison of the results obtained with AbA with those obtained with two other natural products inhibitors, rustmicin and khafrefungin, revealed that while rustmicin appeared to be a reversible, noncompetitive inhibitor of the wild-type enzyme, with a Kiof 16.0 nM, khafrefungin had the kinetic properties of a time-dependent inhibitor and an apparent Kiof 0.43 nM. An evaluation of the efficiencies of these compounds as inhibitors of the mutant enzyme revealed for both a drop in the apparent affinity for the enzyme of more than 2 orders of magnitude.

The oxidative addition of (2,2-dibromovinyl)ferrocene [Br2C=C(H)–Fc] (1) to [Pd(PPh3)4] yields the heterodinuclear σ-alkenyl complex trans-[{Pd(Br)(PPh3)2}–C(Br)=C(H)–Fc] (2). Nucleophilic attack of sodium thiolates on 1 unexpectedly affords the vinyl thioether derivatives (Z)-[(RS)(H)C=C(H)–Fc] (4a: R = Ph; 4b: R = tBu; 4c: R = Et). Complexes 4a and 4c can also be prepared by addition of NaSR across the triple bond of Fc–C≡C–H (3). Addition of an excess of NaSR to 1 affords the dithioether derivatives (Z)-[(RS)(H)C=C(SR)–Fc] (5a: R = Ph; 5b: R = p-tolyl; 5c: R = Et). An addition/elimination sequence is suggested to account for this surprising result. The yield of 5c is very low due to a competing formation of ethynylferrocene (3). Reaction of 5b with [Re(thf)(CO)3(μ-Br)]2 and [PtCl2(PhCN)2] leads to the heterodinuclear chelate complexes [Fc{C(S–p-tolyl)=C(H)(S–p-tolyl)}Re(Br)(CO)3] (6) and [Fc{C(S–p-tolyl)=C(H)(S–p-tolyl)}PtCl2] (7a), respectively. Metathesis of the fluxional compound 7a in the presence of NaI affords [Fc{C(S–p-tolyl)=C(H)(S–p-tolyl)}PtI2] (7b). The electrochemical properties of some of these complexes have been studied by means of cyclic voltammetry, and the molecular structures of 1, 2, 3, 4b, 4c and 6 have been determined by X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The reaction of [Ni(COD)2] with [Cp*2NbTe2H] (1; Cp* = η-C5Me5) in the presence of Ph2PCH2PPh2 (dppm) in boiling toluene gives black-violet [(Cp*2Nb)2NiTe4] (3). If [Cp′2NbTe2H] (2; Cp′ = tBuC5H4) is used under similar conditions dark-brown [(Cp′Nb)2Ni5Te7(dppm)2] (4) is formed. The structures of 3 and 4 have been determined crystallographically. Complex 3 contains a severely distorted NiTe4 tetrahedron to which two niobocene groups are coordinated. Density functional analysis of the electronic structure of the NiTe4 building block shows that it is best described as an [Ni(η2-Te2)2]2– fragment. The structure of 4 reveals the presence of two Ni5 and Te5 tetragonal pyramids stacked into each other in an opposite way. Six of the Te bridges form two triangular faces, each of which is capped by a Cp′Nb fragment. Additionally, two dppm ligands bridge the long Ni–Ni edges of the Ni4 bases. Oxidation of 3 with [(C5H5)2Fe]BPh4 gives paramagnetic [(Cp*2Nb)2NiTe4]BPh4 (6), whereas oxidation with [(C5H5)2Fe]PF6 proceeds with fluoride transfer to give [Cp*2NbF2]PF6 (5). Electrochemical studies of 3 reveal the existence of the redox couples [3]2+/[3]+/[3]0/[3]–/[3]2–. Density functional calculations carried out on the different oxidation states of 3 reveal the following main features: the persistent presence of Nb–Ni bonds and the retention of Te–Te bonds in cationic and neutral species and their breaking off in reduced forms. Irrespective of the initial site of electrochemical attack, the Te atoms and Cp rings are principally affected in the final products.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The heritability of structural properties of the high-carbon steel 1 CS67 during laboratory casting, hot and cold strip rolling, soft annealing, as well as the impact of processing conditions on the final mechanical properties of the strip were studied. Ferrite grain size seems to be more intensively affected by the casting's cooling rate and subsequent heating time than by the phase transformations before conventional rolling. Owing to higher ferrite content resulting from finer austenite grain size, samples obtained after laboratory remelting and casting are characterised by lower yield stress and strength, in combination with higher ductility. A simple model of mean equivalent stress values dependent on temperature, strain and strain rate was developed using the results of hot flat-rolling tests.

Calamagrostis arundinaceaL. (Roth.) and C. villosa(Chaix.) J.F. Gmel are two grass species substituting forest communities on deforested areas in Central Europe. They were exposed to enhanced ultraviolet-B (UV-B, λ = 290–320 nm) radiation during 22 weeks. A system of modulated lamps operating under field conditions was used to simulate a 25 % increase of incident UV-B radiation. CO2assimilation seemed to be limited by a decrease of stomatal conductance (gs) in C. arundinacea, whereas carboxylation activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) was not affected. On the contrary, gsand RuBPCO activity decreased in C. villosa. These physiological adjustments resulted in growth changes; above-ground biomass decreased in C. villosa(prevailing negative effect) and significantly increased in C. arundinacea(prevailing positive effect) in response to enhanced UV-B radiation.

Treatment of 4,4-dichloro-1,1-diphenyl-2-azabuta-1,3-diene [Cl2C=C(H)-N=CPh2] (1) with excess sodium isopropylthiolate or sodium thiophenolate in DMF yielded the 2-azabutadiene derivatives (RS)2C=C(H)–N=CPh2 (2) (2a R = iPr; 2b R = Ph). Nucleophilic attack of the sodium salt of ethyl thioglycolate on 1 afforded as the sole product the six-membered heterocyclic compound ethyl 2-ethoxycarbonylmethylthio-5,5-diphenyl-5,6-dihydro-4H-1,4-thiazine-6-carboxylate (5). The reaction is initiated by substitution of the two vinyl-bound chloro substituents to give {EtO(O=)CCH2S}2C=C(H)–N=CPh2 (2c) as intermediate. A mechanism that accounts for the subsequent cyclisation reaction is proposed. The 2-azabutadiene derivative (PhO)2C=C(H)–N=CPh2 (7) was obtained by the reaction of 1 with sodium phenolate. The regioselectivity of the incoming nucleophile is roughly correlated with its hardness/softness in accord with Pearson’s HSAB principle. The molecular structures of 2a,b, 5 and 7 were determined by single-crystal X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Reactions between the metal(ii) salts [M(CH3CN)n](BF4)2(M = Fe, n= 6; M = Mn, n= 4) and some organic anionic polynitriles were studied. With the pentacyanopropenide anion pcp−[pcp−= (NC)2CC(CN)C(CN)2−], were obtained, according to the experimental conditions, the new complexes [M(pcp)2(H2O)4] (1, M = Fe; 2, M = Mn) and [M(pcp)2] (3, M = Fe; 4= Mn). Use of the hexacyano-3,4-diazahexadienediide anion [(NC)2CC(CN)NNC(CN)C(CN)22−] instead of pcp−did not afford polynitrile metal complexes but led to a new organic derivative 5, of formula C10N8H2. Crystallographic studies indicated that the isostructural compounds 1and 2involve discrete monomeric units with pcp ligands acting with a monodentate coordination mode and having the metal in a pseudooctahedral trans-MN2O4environment; however, a rich hydrogen bond system gives rise to a 3D array. Complex 3, which presents metal in a pseudooctahedral MN6environment, has a 3D structure arising from pcp ligands having an unprecedented μ3-coordination mode. Compound 5is a bicyclic derivative with a pyrazolo[1,5-a]pyrimidine skeleton. In all derivatives, the organic part is essentially planar and involves a strongly delocalized π system. The magnetic properties of the inorganic complexes have been studied in the 2–300 K range. Fit of the magnetic data indicates high spin complexes with weak antiferromagnetic interactions in 2, 3and 4and the presence of a significant zero field splitting of the Fe(ii) ion in 1.

A mathematical model of a catalytic converter for automobile diesel engines that contains zeolites for adsorption of hydrocarbons has been developed. The model includes a description of mass- and heat-transfer resistance at the external surface of the monolith washcoat and internal diffusion within the catalytic washcoat layer. Kinetic parameters for adsorption and oxidation of hydrocarbons [propene (C3H6), decane (C10H22), and toluene (C6H5CH3)], CO oxidation, and NOx adsorption and reduction were evaluated on the basis of dynamic experiments. Model simulations of dynamic operation regimes illustrate the effects of the inlet flow rate, temperature and adsorption capacity on the light-off, integral conversions, and spatiotemporal concentration patterns in the monolith. The effects of varying the transport properties of the washcoat layer (effective diffusion coefficient) and washcoat thickness are also investigated.

Total in vitroactivity of RuBPCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) enzyme was assayed spectrophotometrically by the continuous measurement of 3-phosphoglycerate-dependent NADH oxidation in a coupled enzyme system. RuBPCO activities were found in the ranges 1.01–2.76 and 1.23–3.10 µmol(CO2) m−2s− 1in current Norway spruce needles growing in ambient (AC) and elevated (EC) CO2concentration, respectively. RuBPCO activity in AC needles from the upper layer (U) was 11–15 % higher compared to those from the middle (M) layer, and even 44–56 % higher compared to the lower (L) layer of spruce crown. Over the vegetation season, we observed a highly significant decrease of RuBPCO activity in the EC-U needles from 3.10 (July) to 1.60 (October) µmol(CO2) m−2s−1as a consequence of downward feedback regulation. Moreover, this down-regulation was not caused by a non-specific decrease in total leaf nitrogen content.Total in vitroactivity of RuBPCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) enzyme was assayed spectrophotometrically by the continuous measurement of 3-phosphoglycerate-dependent NADH oxidation in a coupled enzyme system. RuBPCO activities were found in the ranges 1.01–2.76 and 1.23–3.10 µmol(CO2) m−2s− 1in current Norway spruce needles growing in ambient (AC) and elevated (EC) CO2concentration, respectively. RuBPCO activity in AC needles from the upper layer (U) was 11–15 % higher compared to those from the middle (M) layer, and even 44–56 % higher compared to the lower (L) layer of spruce crown. Over the vegetation season, we observed a highly significant decrease of RuBPCO activity in the EC-U needles from 3.10 (July) to 1.60 (October) µmol(CO2) m−2s−1as a consequence of downward feedback regulation. Moreover, this down-regulation was not caused by a non-specific decrease in total leaf nitrogen content.

Four deuterium‐labelled ABA catabolites of high isotopic purity were prepared for hormone profiling studies using HPLC‐ESI‐MS‐MS. The catabolites, namely [7′,7′,7′‐d3]‐PA, [7′,7′,7′‐d3]‐DPA, [5,8′,8′,8′‐d4]‐7′‐hydroxyABA and [4,5,8′,8′,8′‐d5]‐ABA glucose ester were prepared either by biotransformation or chemical synthesis starting with labelled ABA. The labelled compounds are employed as internal standards for plant hormone profiling by liquid chromatography–electrospray–tandem mass spectrometry. Copyright © 2005 John Wiley & Sons, Ltd.

In a previous paper (Grof, Z.; Kosek, J.; Marek, M. Morphogenesis model of growing polyolefin particles. AIChE J., accepted), we have introduced the model of the morphological evolution of polyolefin particles in catalytic polymerization reactors. The model considers the polyolefin particle to consist of a large number of microelements with viscoelastic interactions acting among them. Here we present the results of the systematic mapping from the parametric space of catalyst activity, reaction conditions, mass transport resistance, and viscoelastic properties of polyolefins into the space of possible morphological developments, such as the formation of hollow particles, particles with macrocavities, regular or irregular replication of particle shape during its growth, highly porous or compact particles, the formation of fine particles, etc. The predicted particle morphologies are compared with experimental findings. We focus on the effect of temperature on the morphogenesis of polyolefin particles and identify the reaction conditions leading to the disintegration of the growing particle into fine particles, which is the unwanted phenomenon observed in industrial reactors. The causes of different pore space morphologies of Ziegler−Natta and metallocene-born polyolefin particles are also investigated.

Two models of catalytic monolith reactor with diffusion in the washcoat are described, employing the nonstationary kinetics of CO and hydrocarbon oxidation, NOx reduction, and oxygen storage with 23 reaction steps. The first model describes the dynamic behavior in a short monolith (recirculation reactor or CSTR), and the second one is a spatially two-dimensional nonstationary model of the monolith with plug flow. The models are used to demonstrate the qualitative agreement between the observed nonlinear dynamics of CO oxidation, including hysteresis and periodic and period-doubled oscillations, and earlier experiments. The effects of transport parameters within the washcoat on the monolith lightoff and on the outlet conversions are simulated. Computed spatiotemporal concentration patterns of reaction intermediates within the washcoat layer are used to discuss the oxidation and reduction functions of the three-way-catalyst monolith.

Genuine heteroleptic neodymium and samarium complexes of formula [Cp*′Ln{(p‐tol)NN}(BH4)] (Cp*′ = C5Me4(nPr), (p‐tol)NN = (p‐tol)NC(Me)CHC(Me)N(p‐tol), Ln = Sm: 1 a, Ln = Nd: 1 b) have been synthesized for the first time. These unprecedented homologues of early lanthanocenes are prepared by a metathetic reaction between their monocyclopentadienylbisborohydrido precursors with the corresponding potassium diketiminate. Both complexes were obtained in good yields and were characterized by 1H NMR spectroscopy and elemental analysis. Complex 1 ahas an non‐solvated dimeric structure, as indicated by its crystallographic data. The chloroneodymium analogue [Cp*′Nd{(p‐tol)NN}(Cl)] (2 b) was only obtained as a part of a mixture. Analysis of crystals of 2 bby X‐ray diffraction revealed a molecular structure very similar to that of 1 a. Preliminary isoprene polymerization experiments were carried out with 1 bin the presence of an alkylmagnesium coactivator. The resulting bimetallic Nd/Mg system behaves as an efficient and highly stereospecific catalyst with the synthesis of trans‐1,4‐polyisoprene with more than 98 % regularity. The control of the polymer structure is related to the steric hindrance around the lanthanide atom.

The chromatographic performance with respect to the flow behavior and dispersion in fixed beds of nonporous and macroporous particles (having mean intraparticle pore diameters of 41, 105, and 232 nm) has been studied in capillary HPLC and electrochromatography. The existence of substantial electroosmotic intraparticle pore flow (perfusive electroosmosis) in columns packed with the macroporous particles was found to reduce stagnant mobile mass transfer resistance and decrease the global flow inhomogeneity over the column cross-section, leading to a significant improvement in column efficiency compared to capillary HPLC. The effect of electroosmotic perfusion on axial dispersion was shown to be sensitive to the mobile phase ionic strength and mean intraparticle pore diameter, thus, on an electrical double layer interaction within the particles. Complementary and consistent results were observed for the average electroosmotic flow through packed capillaries. It was found to depend on particle porosity and distinct contributions to the electrical double layer behavior within and between particles. Based on these data an optimum chromatographic performance in view of speed and efficiency can be achieved by straightforward adjustment of the electrolyte concentration and characteristic intraparticle pore size.

The preparation of a family of dinuclear monocyclopentadienyl imidoniobium and -tantalum complexes was achieved by two different synthetic routes. The diimido complexes [{M(Cp')Cl2}2(μ-1,i-NC6H4N)] [Cp' = η⁵-C5H4SiMe3, M = Nb, i = 4 (1); Cp' = η⁵-C5H4SiMe3, M = Nb, i = 3 (2); Cp' = η⁵-C5H4SiMe3, M = Nb, i = 2 (3); Cp' = η⁵-C5Me5, M = Nb, i = 4 (4); Cp' = η⁵-C5Me5, M = Nb, i = 3 (5); Cp' = η⁵-C5H4SiMe3, M = Ta, i = 4 (6); Cp' = η⁵-C5H4SiMe3, M = Ta, i = 3 (7)] were prepared by the reaction of one equivalent of the trichloro precursor [{MCl3}2(μ-1,i-NC6H4N)] (M = Nb, Ta, i = 4, 3 or 2) with two equivalents of either C5H4(SiMe3)2 or C5Me5(SiMe3). Complexes 1−7 can also be prepared by the reaction of two equivalents of [MCp'Cl4] (Cp' = η⁵-C5H4SiMe3, M = Nb, Ta; Cp' = η⁵-C5Me5, M = Nb, Ta) with one equivalent of the corresponding aniline compound, N,N,N',N'-tetrakis(trimethylsilyl)-1,4-, -1,3-, or -1,2-phenylenediamine, respectively. The synthesis of [{Ta(Cp')Cl2}2(μ-1,i-NC6H4N)] [Cp' = η⁵-C5Me5, i = 4 (8); Cp' = η⁵-C5Me5, i = 3 (9)] was only successful with the second preparative method. The reaction of 1, 2 and 8 with alkylating reagents gave the corresponding tetraalkyl derivatives, [{M(Cp')R2}2(μ-1,i-NC6H4N)] [Cp' = η⁵-C5H4SiMe3, M = Nb, R = Me, i = 4 (10); Cp' = η⁵-C5H4SiMe3, M = Nb, R = CH2SiMe3, i = 4 (11); Cp' = η⁵-C5H4SiMe3, M = Nb, R = CH2Ph, i = 4 (12); Cp' = η⁵-C5H4SiMe3, M = Nb, R = Me, i = 3 (13); Cp' = η⁵-C5H4SiMe3, M = Nb, R = CH2SiMe3, i = 3 (14); Cp' = η⁵-C5H4SiMe3, M = Nb, R = CH2Ph, i = 3 (15); Cp' = η⁵-C5Me5, M = Ta, R = Me, i = 4 (16); Cp' = η⁵-C5Me5, M = Ta, R = CH2SiMe3, i = 4 (17); Cp' = η⁵-C5Me5, M = Ta, R = CH2Ph, i = 4 (18)]. The alkylated complexes with other stoichiometries, [{M(Cp')(Me)(X)}2(μ-1,4-NC6H4N)] [Cp = η⁵-C5H4SiMe3, M = Nb, X = Cl (19); Cp = η⁵-C5H4SiMe3, M = Nb, X = NMe2 (20); Cp = η⁵-C5Me5, M = Ta, X = Cl (21)], were also prepared. The molecular structures of complexes 1, 8 and 17 were determined by single-crystal X-ray diffraction studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Sphingolipid precursors, namely, ceramide and long-chain base phosphates (LCBPs), are important growth regulators with often opposite effects on mammalian cells. A set of enzymes that regulate the levels of these precursors, referred to as a ceramide/LCBP rheostat, is conserved in all eukaryotes. In order to gain further insight into the function of the rheostat in Saccharomyces cerevisiae, we searched for mutants that are synthetically lethal with a deletion of the LCB3 gene encoding LCBP phosphatase. In addition to acquiring expected mutants lacking the LCBP lyase, the screen revealed elo3 (sur4) mutants that were defective in fatty acid elongation and cka2 mutants lacking the alpha' subunit of the protein kinase CK2 (casein kinase). Both mutations affected the in vivo activity of the acyl coenzyme A (acyl-CoA)-dependent and fumonisin B(1)-sensitive ceramide synthase (CS). The Elo3 protein is necessary for synthesis of C(26)-CoA, which in wild-type yeast is a source of C(26) fatty acyls found in the ceramide moieties of all sphingolipids. In the in vitro assay, CS had a strong preference for acyl-CoAs containing longer acyl chains. This finding suggests that a block in the formation of C(26)-CoA in yeast may cause a reduction in the conversion of LCBs into ceramides and lead to an overaccumulation of LCBPs that is lethal in strains lacking the Lcb3 phosphatase. In fact, elo3 mutants were found to accumulate high levels of LCBs and LCBPs. The cka2 mutants, on the other hand, exhibited only 25 to 30% of the in vitro CS activity found in wild-type membranes, indicating that the alpha' subunit of CK2 kinase is necessary for full activation of CS. The cka2 mutants also accumulated high levels of LCBs and had elevated levels of LCBPs. In addition, both the elo3 and cka2 mutants showed increased sensitivity to the CS inhibitors australifungin and fumonisin B(1). Together, our data demonstrate that the levels of LCBPs in yeast are regulated by the rate of ceramide synthesis, which depends on CK2 kinase activity and is also strongly affected by the supply of C(26)-CoA. This is the first evidence indicating the involvement of protein kinase in the regulation of de novo sphingolipid synthesis in any organism.

The organo-diimido tantalum complexes [{Ta(L₂)Cl₃}₂(μ-1,n-NC₆H₄N)], L = MeCN (1) and 4-tBupy (2), have been prepared by two alternative experimental methods: (1) the initial formation of the corresponding TaCl₅·L adduct, L = 4-tBupy or CH₃CN, followed by addition of the appropriate phenylenediamine, or (2) the initial formation of the corresponding organo-diimido species and subsequent addition of the ligand L. These complexes, as well as some related niobium complexes, were alkylated using the appropriate Grignard reagent to afford the alkyl-containing complexes [{M(L)R₃}₂(μ-1,n-NC₆H₄N)] (4, 5, 6, 7, 8, 9) (M = Nb, Ta; n = 3, 4; L = MeCN, R = CH₂SiMe₃, CH₂CMe₃, CH₂CMe₂Ph). These complexes can be prepared by treating the corresponding chloro-complexes with dialkylmagnesium reagents MgR₂(THF)₂. Niobium complexes containing THF ligands, i.e. [{Nb(THF)R₃}₂(μ-1,3-NC₆H₄N)] (10, 11) (R = CH₂SiMe₃, CH₂CMe₃), were isolated by using THF as the solvent and also from the acetonitrile-containing complexes 8b and 9b by simply adding THF. The complex [{Nb(CH₂CMe₂Ph)₃}₂(μ-1,4-NC₆H₄N)] (12a) was prepared by addition of the corresponding Grignard reagent to a suspension of [{Nb(MeCN)₂Cl₃}₂(μ-1,4-NC₆H₄N)] in THF. The reaction of complexes [{M(MeCN)₂Cl₃}₂(μ-1,n-NC₆H₄N)] (M = Ta, Nb; n = 3, 4) with Li[C₅H₄SiMe₃] was carried out and afforded the tetrakis-cyclopentadienyl-diimido complexes [{M(η5-C₅H₄SiMe₃)₂Cl}₂(μ-1,n-NC₆H₄N)] [M = Ta, n = 4 (13a); M = Ta, n = 3 (13b); M = Nb, n = 4 (14a); M = Nb, n = 3 (14b)]. The structure of 13a has been solved by X-ray diffraction. Finally, we have performed the reactions between the diimido-containing compounds [{M(MeCN)₂Cl₃}₂(μ-1,n-NC₆H₄N)] (M = Ta, Nb; n = 3, 4) and the lithium benzamidinate Li[PhC(NSiMe₃)₂] to afford the benzamidinate-containing complexes [{M[PhC(NSiMe₃)₂]₂Cl}₂(μ-1,n-NC₆H₄N)] [M = Ta, n = 4 (15a); M = Ta, n = 3 (15b); M = Nb, n = 4 (16a)]. The structures of the different families of compounds were determined by spectroscopic methods.

4,4-Dichloro-1,1-diphenyl-2-azabuta-1,3-diene (1) oxidatively adds to [Pd(PPh3)4] and [Pt(C2H4)(PPh3)2] giving rise to the σ-alkenyl complexes trans-[MCl{[C(Cl)=C(H)−N=CPh2]}(PPh3)2] (2a: M = Pd; 2b: M = Pt). When 1 is treated with [Pd(PPh3)4] in a 1:2 ratio in refluxing toluene, the dimetallic μ-vinylidene complex [(PPh3)ClPd{μ-[C=C(H)−N=CPh2]}PdCl(PPh3)2] (3) is formed. In this fluxional compound, a PPh3 ligands migrates in a reversible manner between the two Pd centers. Substitution of the PPh3 ligands of 3 by 2 equiv. of Ph2PCH2PPh2 affords the A-frame complex [ClPd(μ-dppm)2{μ-[C=C(H)−N=CPh2]}PdCl] (4). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The complex [Cp*{C5H4(CH2CH2NMe2)}TaCl2] (1) was synthesised by reaction of the lithium salt LiC5H4(CH2CH2NMe2) with the tantalum compound [Cp*TaCl3(PMe3)]. Reduction of 1 with NaAl(H)2(OCH2CH2OMe)2 leads to the trihydride derivative [Cp*{C5H4(CH2CH2NMe2)}TaH3] (2). The oxidation of 2 in THF with ferrocenium ion leads to a cationic dihydride intermediate [Cp*{C5H4(CH2CH2NMe2)}TaH2]PF6 (3) with an intramolecular stabilization by the aminoethyl side-chain of the cyclopentadienyl ligand. The hemilabile character of the functionalised cyclopentadienyl ligand was checked by treating 3 with electron-donating ligands (e.g. phosphanes, sulfides, anions); in all cases, no displacement of the amino group was observed. When treated with HBF4, 2 undergoes a loss of the hydride and the resulting cation can be isolated as a solvento adduct by carrying out the reaction in dimethyl sulfide. Acidolysis of 2 in the presence of an excess of trifluoroacetic acid affords the compound [Cp*{C5H4(CH2CH2NHMe2)}TaH(OCOCF3)2](CF3COO) (5). Microanalytical and NMR spectroscopic data for these complexes are given. The X-ray crystal structures are reported for [Cp*{C5H4(CH2CH2NMe2)}TaH2]PF6 (3) and [Cp*{C5H4(CH2CH2NHMe2)}TaH(OCOCF3)2](CF3COO) (5). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Reaction of [Cp'2NbH3] (Cp' = tBuC5H4) with Te powder in THF gives [Cp'2Nb(Te2)H] (1) and [Cp'6Nb4Te4O] (2). The yield of 1 varies between 10 and 81% depending on the degree of oxygen contamination of the reagents. Complexes 1 and 2 react with [Cr(CO)5THF] to give [Cp'2Nb(Te2)H·Cr(CO)5] (3) and [Cp'6Nb4Te4O·2Cr(CO)5] (4), respectively. The crystal structures of 2−4 have been determined. In 3 a Te2 unit and an H ligand are coordinated to a bent niobocene moiety; the Cr(CO)5 group is attached to the lateral Te atom. The molecular cores of 2 and 4 are practically identical in that they contain two planar Nb2Te2 rings connected by a nearly linear oxygen bridge. Each of the “outer” Nb atoms bears two Cp' ligands, whereas the “inner” Nb atom only has one such ligand. An additional structural feature in 4 is two Cr(CO)5 groups, attached to one Te bridge of each Nb2Te2 ring. Thermolysis of 3 leads to the formation of diamagnetic [Cp'4Nb2Te2] (5), which also contains a planar Nb2Te2 core. The relatively long transannular Nb−Nb distance (3.647 Å) is consistent, according to DFT calculations, with a through-space Nb−Nb coupling. Complex 5 reacts with CH3I with successive methylation of both Te bridges to give [Cp'4Nb2Te(CH3Te)]I ([6]I) and [Cp'4Nb2(CH3Te)2]I2 ([7]I2). The crystal structure of [7]I2 may be derived from that of 5, the incoming CH3 groups being fixed at the Te bridges in a trans position. ¹H NMR spectroscopic investigations reveal a restricted rotation around the Cp'−Nb bonds in 2 and 5 at −90 °C and in 4 and [7]I2 at ambient temperature. Electrochemical studies have been carried out on 5, [6]I, and [7]I2, showing that all compounds undergo two reversible one-electron reduction steps. The reduction potential decreases by ca. 1.6 V when going from 5 to [7]I2. There is also a clear linear correlation between the reduction potentials measured for 5 to [7]I2 and the energies of the corresponding LUMO’s calculated at the DFT/B3LYP level. These LUMO’s bear some 70% contribution from both Nb atoms and, consequently, the reduction processes mainly operate at both metallic centers. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Analysis of penicillin G hydrolysis in a membrane reactor with membrane-entrapped penicillin G acylase is performed using a mathematical model of the reactor system. An electric field imposed to the reactor is considered to enhance transport rates of reaction components and reaction rate. Diffusion, electrophoretic migration and electro-osmotic flux across the membrane are considered. The analysis focuses on possible effects of the principal operational parameters (electric field intensity, inlet substrate concentration, membrane thickness) on reactor performance. Multiplicities of steady states are frequently encountered. The membrane reactor performance can be easily targeted towards the required reaction regime by applying a constant or periodically varying electric field to the system. The periodic alternation of the polarity of the electric field substantially increases the effectiveness factor of penicillin hydrolysis compared with the steady state operation. Proper adjustments of electric field intensity may also compensate for the decay in enzyme activity.
© 2001 Society of Chemical Industry

The reactions of the copper(I) derivative [CuL(THF)(CH 3 CN)]PF 6 ( 1 ), in which L is the di-imine/pyridine ligand 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine, with different β-diketones (2,4-pentanedione (acacH), 1,3-diphenyl-1,3-propanedione (dbm)) yielded the new Cu(I) salt [CuL′ 2 ]PF 6 ( 2 ) (L′: 2-[acetyl]-6-[1-(2,6-diisopropylphenylimino)ethyl]pyridine). These reactions of β-diketones with a di-imine/pyridine ligand co-ordinated to a Cu(I) centre constitute the first example of a partial hydrolysis of such a Schiff base within the inner sphere of a Cu centre. Compound 2 ·acaH has been characterised by X-ray crystallography.

The problem of controlling temperature profile along a monolithic reactor in which an exothermic reaction (selective catalytic reduction of NOxby hydrocarbons) takes place is considered. Several solutions are proposed and compared. It is shown that a near‐optimum temperature profile can be achieved by two rather different approaches – one based on periodic switching of a hot reactant and a cold inert stream between two thermally coupled monoliths, and one based on pre‐mixing the reactant and coolant streams. An adaptive control scheme based on model‐predictive control is proposed and shown to be efficient for the case of time‐variable properties of the reactant stream.

A series of new 2substituted thiazolidine4carboxamide derivatives which have potentially useful immunological properties, have been synthesized in a stereoselective manner by coupling 2subsituted thiazolidine4carboxylic acids with amines or amino esters. The structure of these compounds was established by combination of NMR methods and by Xray analysis.

The propagation of arsenous acid−iodate reaction fronts of different net stoichiometries in externally applied dc electric fields is studied for a range of both electric field intensities and initial compositions of the reacting mixture (represented by the stoichiometric factor S0). Regions of three different types of net stoichiometry in the parametric space E/V vs S0, where E is the intensity of the applied electric field and V the reaction front propagation velocity, are determined both experimentally and by analyzing a reaction−diffusion−migration model that includes a realistic kinetic scheme of the reaction studied. Both agreement with and discrepancies between the theoretical predictions and experimental findings are discussed.

Results of post test simulation of the PANDA passive containment cooling (PCC) steady-state tests (S-series tests), performed at the PANDA facility at the Paul Scherrer Institute, Switzerland, are presented. The simulation has been performed using the computer code SPECTRA, a thermal-hydraulic code, designed specifically for analyzing containment behavior of nuclear power plants.Results of the present calculations are compared to the measurement data as well as the results obtained earlier with the codes MELCOR, TRAC-BF1, and TRACG. The calculated PCC efficiencies are somewhat lower than the measured values. Similar underestimation of PCC efficiencies had been obtained in the past, with the other computer codes. To explain this difference, it is postulated that condensate coming into the tubes forms a stream of liquid in one or two tubes, leaving most of the tubes unaffected. The condensate entering the water box is assumed to fall down in the form of droplets. With these assumptions, the results calculated with SPECTRA are close to the experimental data.It is concluded that the SPECTRA code is a suitable tool for analyzing containments of advanced reactors, equipped with passive containment cooling systems.

The reaction of some sodium alkoxides with 4,4-dichloro-1,1-diphenyl-2-azabuta-1,3-diene is described. Whereas sodium methoxide, ethoxide or isopropoxide leads to 1,3-bis(alkoxy)- and/or 1,3,4-tris(alkoxy)-2-azabut-2-enes, the sodium salt of ethyl glycolate gives a Δ²-oxazoline. Mechanisms for the formation of these products are proposed.

The Czech Boron Neutron Capture Therapy (BNCT) facility works by an epithermal neutron beam installed at the LVR-15 reactor at Rez near Prague. Several configurations of moderating and shielding materials have been designed in order to ensure appropriate parameters of the beam. The beam filter consists of cylindrical layers of Al, AlF3and Ti. To decrease the gamma two layers of Pb are implemented. The filter geometry and composition has been optimized with the aim to increase the epithermal neutron fluence rate and decrease the fast neutron dose rate using the MCNP-4B Monte Carlo code with the DLC-189 library.Suitable patterns of the reactor core were also studied especially in regard to a possible installation of fuel units close to the filter input. Results of calculations show that the optimized variant of the reactor core is able to increase the intensity of the fast neutron source incident to the filter by a factor of 2.0.An experimental verification of the beam parameters was performed using different measurement techniques. The neutron energy spectrum was measured with a set of activation foils, by a Bonner spheres spectrometer and a fast neutron spectrometer with a stilbene crystal. The fast neutron kerma rate was calculated from the spectral measurement. Al-P TLD were used to measure the photon absorbed dose.The beam parameters were measured at 10 MW and were found as follows: the epithermal neutron fluence rate (an energy range from 1 eV to 10 keV) of 9.29 × 10l2m−2s−1, the fast neutron kerma rate in tissue of 2.63 Gy h−1and the incident gamma dose rate in tissue of 2.9 Gy h−1.