Three novel metal-organic-frameworks (MOFs) based on dysprosium as the metal and dicarboxylic ligands have been solvothermally synthesized with the aim of studying and modulating their magnetic ...properties according to the variation of the distances between metal centers. These materials display intense photoluminescence properties in the solid state at room temperature. In addition, a very interesting property of compound 1 is that it exhibits slow relaxation of magnetization with an activation energy barrier of 32 K. Magneto-structural correlations have been analyzed.
The rimJ gene, which codes for a crotonyl-CoA carboxylase/reductase, lies within the biosynthetic gene cluster for two polyketides belonging to the polyene macrolide group (CE-108 and rimocidin) ...produced by Streptomyces diastaticus var. 108. Disruption of rimJ by insertional inactivation gave rise to a recombinant strain overproducing new polyene derivatives besides the parental CE-108 (2a) and rimocidin (4a). The structure elucidation of one of them, CE-108D (3a), confirmed the incorporation of an alternative extender unit for elongation step 13. Other compounds were also overproduced in the fermentation broth of rimJ disruptant. The new compounds are in vivo substrates for the previously described polyene carboxamide synthase PcsA. The rimJ disruptant strain, constitutively expressing the pcsA gene, allowed the overproduction of CE-108E (3b), the corresponding carboxamide derivative of CE-108D (3a), with improved pharmacological properties.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Rh(nbd)Cl2 (nbd=norbornadiene) reacts with quinoline‐8‐carbaldehyde (C9H6NCHO) and pyrazole (Hpz) affording, depending on Rh/Hpz ratio, acyl‐alkyl Rh(μ‐Cl)(C9H6NCO)(Hpz)(σ‐C7H9)2 (1) or ...RhCl(C9H6NCO)(Hpz)2(σ‐norbornenyl) (2), stereoselectively as confirmed by DFT calculations. Hydrogen bond between NH‐pyrazole and O‐acyl occurs. 1 and 2 react with diphenylphosphine oxide (SPO) giving 16e RhCl(C9H6NC(nbyl))(Ph2PO)(Hpz) (3) through SPO κ1‐P‐coordination, C−C bond coupling between acyl and norbornenyl and outer‐sphere O(P)‐to‐O(C) hydrogen transfer. 3 shows distorted trigonal bipyramidal structure with weak intramolecular (C)−OH⋅⋅⋅O(=P) and NH⋅⋅⋅Cl hydrogen bonds. DFT calculations indicate this 16e structure being favoured by σ‐ and π‐type orbital multi‐overlapping between pyrazole and both the OH⋅⋅⋅O and chlorine and by intermolecular forces in the crystal. Solutions of 3 contain an equilibrium between trigonal bipyramid and a square‐planar pyramid with OH interacting with phosphoryl and NH, confirmed by DFT 13C NMR calculations. 1 is very efficient homogeneous catalyst for H3N−BH3 hydrolysis to release hydrogen under air.
Acyl‐pyrazole complex efficient homogeneous catalyst for hydrolytic H2 release from ammonia‐borane. PPh2(O)promotes tandem C−C coupling/outer sphere hydrogen transfer and stable pyrazole 16e species. DFT studies allow understanding experimental X‐ray structures and observed species in solution.
The molecule 4-(diphenylphosphino)benzoic acid (dpa) anchored on the surface of magnetite nanoparticles permits the easy capture of palladium ions that are deposited on the surface of the magnetite ...nanoparticles after reduction with NaBH 4 . Unexpectedly, a significant fraction of dpa is removed in this process. Samples of Fe 3 O 4 dpa@Pd x containing different Pd loadings ( x = 0.1, 0.3, 0.5 and 1.0 wt%) were prepared, and their catalytic efficiency for the Suzuki C–C coupling reaction was studied. The best catalyst was Fe 3 O 4 dpa@Pd 0.5 , which gave the highest TOF published to date for the reaction of bromobenzene with phenylboronic acid in a mixture of ethanol/water (1/1). Interestingly, the same reaction carried out in water also produced excellent yields of the resulting C–C coupling product. The behaviour of other bromide aryl molecules was also investigated. The best catalytic results for the aqueous phase reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) were obtained using Fe 3 O 4 dpa@Pd 0.1 . The presence of Pd SACs (single atom catalysts) seems to be responsible for this performance. In contrast, the same Fe 3 O 4 dpa@Pd 0.1 catalyst is absolutely inactive for the hydrogenation of styrene in ethanol.
Under physiological conditions, strength and persistence of memory must be regulated in order to produce behavioral flexibility. In fact, impairments in memory flexibility are associated with ...pathologies such as post-traumatic stress disorder or autism; however, the underlying mechanisms that enable memory flexibility are still poorly understood. Here, we identify transcriptional repressor Wilm's Tumor 1 (WT1) as a critical synaptic plasticity regulator that decreases memory strength, promoting memory flexibility. WT1 is activated in the hippocampus following induction of long-term potentiation (LTP) or learning. WT1 knockdown enhances CA1 neuronal excitability, LTP and long-term memory whereas its overexpression weakens memory retention. Moreover, forebrain WT1-deficient mice show deficits in both reversal, sequential learning tasks and contextual fear extinction, exhibiting impaired memory flexibility. We conclude that WT1 limits memory strength or promotes memory weakening, thus enabling memory flexibility, a process that is critical for learning from new experiences.
We report the formation of a novel multifunctional metal–organic framework (MOF) based on dysprosium( iii ) ions using pyrene-1,3,6,8-tetrasulfonate (pytet) 4− as a ligand, synthesized using a soft ...hydrothermal route. This material shows a two-dimensional network with small channels along a crystallographic axis and displays intense photoluminescence properties in the solid state at room temperature due to the pyrene derivative ligand. The magnetic properties of this 2D-MOF are also accomplished, confirming slightly frequency-dependent out of phase signals under an applied field of 1000 Oe.
We have designed and synthesized eight isostructural 1D coordination polymers (CPs) with the general formula {Ln(aapc)3(DMF)}n where Ln(iii) = Y (2), La (3), Nd (4), Eu (5), Gd (6), Tb (7), Dy (8), ...Er (9); and aapc = 3-((anthraquinone-1-yl)amino)propanoate. These CPs consist of Ln-carboxylate infinite rods in which the bulky anthraquinone scaffolds arise from it in such a way that the resulting supramolecular packing exhibits isolated 1D chains. Solution structures have been corroborated through NMR methods including PGSE and EXSY NMR studies and, due to the presence of lanthanide ions, magnetic and luminescence properties have been studied. Alternating current magnetic measurements of compound 8 show slow relaxation of the magnetization, a characteristic of single molecule magnets (SMMs). The evaluation of solid-state photophysical properties reveals that the aapc scaffold sensitizes lanthanide(iii) based emission of compounds 4-9 both in the visible and near-infrared (NIR) regions at 10 K.
Turboroundabouts Vasconcelos, Luís; Silva, Ana B.; Seco, Álvaro M. ...
Transportation research record,
01/2014, Letnik:
2402, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A “turboroundabout” is a variation of the conventional multilane roundabout in which spiral road markings and raised lane dividers force drivers to follow a specific path according to their intended ...destination. This geometry eliminates weaving and cut-in conflicts by guiding drivers continuously from entry to exit. Turboroundabouts were conceived with the main aim of improving safety, but their practical benefits are relatively unknown. Likewise, the few existing studies on turboroundabouts do not allow definitive conclusions to be drawn about the delay and emissions performance characteristics of turboroundabouts; further research is needed. This research focused on the use of appropriate modeling methodologies to understand the effects of turboroundabouts on capacity, safety, and emissions in comparison with the effects of conventional single-lane and double-lane roundabouts. The results indicate that turboroundabouts have capacity levels comparable to those of two-lane roundabouts but are less robust concerning the directional split of the entry traffic; turboroundabouts lead to fewer traffic conflicts, but the traffic conflicts that do occur are more severe. The results also show that the implementation of turboroundabouts provides no advantages for emissions when the main concerns are carbon dioxide and oxides of nitrogen.
Importantly, in the three cases, ZIKV infection occurred in the first trimester of pregnancy. ...the three cases were symptomatic and laboratory confirmed. ...the high cross reactivity between dengue ...and ZIKV induced antibodies and the absence of available neutralization tests against DENV in our setting hampered a more precise classification of the group of probable ZIKV infections. ...other relevant risk factors such as precise duration of the trip or stay in the endemic areas, magnitude of the ZIKV circulation in each country at the time of visit and use of repellents or other measures against mosquito bites, were not systematically assessed.
The dihydridoirida-β-diketone IrH2{(PPh2(o-C6H4CO))2H} (2) has been used as a homogeneous catalyst for the hydrolysis of ammonia- or amine-boranes to generate up to 3 equivalents of hydrogen in the ...presence of air. When using 0.5 mol% loading of 2, dimethylamine-borane is hydrolysed completely within 8 min at 30 °C and maintains its activity in consecutive runs. Ammonia-borane or tert-butylamine-borane is hydrolysed completely within 32 or 25 min respectively. Triethylamine-borane fails to be hydrolysed. Kinetic studies suggest a sequence of two consecutive first-order reactions, in which an intermediate builds up and finally falls, with the first step being the rate controlling step. ΔH1(‡) are in the range 65-85 kJ mol(-1) and negative values of ΔS1(‡) are obtained. A multinuclear NMR study of the catalyzed reaction shows the formation of a resting state (A) of the active catalyst proposed to be of the hydridodiacyl type IrH(PPh2(o-C6H4CO))2(solvent) with a hydride trans to the acyl group. In the absence of substrate a dormant species (B) is formed. By the reaction of hydridoirida-β-diketones with ammonia, the hydridoirida-β-ketoimine IrHCl{(PPh2(o-C6H4CO))(PPh2(o-C6H4CNH))H} (3) and the hydridobis(acylphosphane)aminoiridium(III) complex IrH(PPh2(o-C6H4CO))2(NH3) (4), with a hydride trans to phosphane, are formed. Aromatic amines such as aniline or anisidines afford cationic IrH{(PPh2(o-C6H4CO))2H}(C6H4RNH2)ClO4 (R = H (6); p-MeO (7); o-MeO (8)) hydridoirida-β-diketones with a coordinated amine group trans to the hydride. The dormant species B is proposed to be of the hydridobis(acylphosphine)aminoiridium(III) type with a hydride trans to the amine group.
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