The synthesis of single enantiomers of trans-alkene-containing mycolic acids

We report routes to single enantiomers of hydroxy and ketomycolic acids containing an α-methyl-trans-alkene unit.     

Observation of a superfluid component within solid helium

We demonstrate by neutron scattering that a localized superfluid component exists at high pressures within solid helium in aerogel. Its existence is deduced from the observation of two sharp phonon-roton spectra which are clearly distinguishable from modes in bulk superfluid helium. These roton excitations exhibit different roton gap parameters than the roton observed in the bulk fluid at freezing pressure. One of the roton modes disappears after annealing the samples. Comparison with theoretical calculations suggests that the model that reproduces the observed data best is that of superfluid double layers within the solid and at the helium-substrate interface.     

Synthesis of Furo[2,3‐d]pyridazin‐4(5H)‐one and Its N(5)‐Substituted Derivatives

We report the efficient preparation of furo[2,3‐d]pyridazin‐4(5H)‐one and its N‐substituted derivatives starting from methyl 2‐methylfuran‐3‐carboxylate. The Me group was converted to the aldehyde group, which was then condensed with hydrazine derivatives. Then, the ester functionalities were hydrolyzed to the corresponding acids, followed by treatment with SOCl₂ to give N‐substituted furopyridazinone derivatives.     

Synthèse dc la pyrido[2,3-f] phtalazine et des diformyl-6,7; -4,6; -4,7; -2,4 quinoleines

This article describes the synthesis of a new heterocycle, pyrido[2,3,f]phtalazine and three new diformylquinolincs.     

Synthèse des pyrido[2,3-d] el [3,2-d] -s-triazolo[3,4-f] pyrimidines el de (pyrazolyl-1')-4 pyrido[2,3-d] et [3,2-d] pyrimidines

The synthesis of two new heterocycles is described: pyrido-[2,3-d]-.s-triazolo[ 3,4-f] pyrimidine and pyrido[3,2-d]-.s-triayzolo-[3,4-f] pyrimidine. 4-[I'-Pyrazolyl]pyrido[2,3-d]pyrimidines and 4-[1′-pyrazoly1] pyrido[ 3,2-d] pyrimidine are obtained by the action of 4-hydrazinopyrido[2,3-d]pyrimidine and 4-hydrazinopyrido-[3,2-d]pyrimidine with several β-diketones.     

The developmental pattern of stimulus and response interference in a color-object Stroop task: an ERP study

Background

Several studies have shown that Stroop interference is stronger in children than in adults. However, in a standard Stroop paradigm, stimulus interference and response interference are confounded. The purpose of the present study was to determine whether interference at the stimulus level and the response level are subject to distinct maturational patterns across childhood. Three groups of children (6–7 year-olds, 8–9 year-olds, and 10–12 year-olds) and a group of adults performed a manual Color-Object Stroop designed to disentangle stimulus interference and response interference. This was accomplished by comparing three trial types. In congruent (C) trials there was no interference. In stimulus incongruent (SI) trials there was only stimulus interference. In response incongruent (RI) trials there was stimulus interference and response interference. Stimulus interference and response interference were measured by a comparison of SI with C, and RI with SI trials, respectively. Event-related potentials (ERPs) were measured to study the temporal dynamics of these processes of interference.

Results

There was no behavioral evidence for stimulus interference in any of the groups, but in 6–7 year-old children ERPs in the SI condition in comparison with the C condition showed an occipital P1-reduction (80–140 ms) and a widely distributed amplitude enhancement of a negative component followed by an amplitude reduction of a positive component (400–560 ms). For response interference, all groups showed a comparable reaction time (RT) delay, but children made more errors than adults. ERPs in the RI condition in comparison with the SI condition showed an amplitude reduction of a positive component over lateral parietal (-occipital) sites in 10–12 year-olds and adults (300–540 ms), and a widely distributed amplitude enhancement of a positive component in all age groups (680–960 ms). The size of the enhancement correlated positively with the RT response interference effect.

Conclusion

Although processes of stimulus interference control as measured with the color-object Stroop task seem to reach mature levels relatively early in childhood (6–7 years), development of response interference control appears to continue into late adolescence as 10–12 year-olds were still more susceptible to errors of response interference than adults.     

Dynamic singularity in multicomponent glass-forming metallic liquids

In the liquid state, glass-forming Ni59.5Nb40.5 and Ni60Nb34.8Sn5.2 alloys exhibit an extraordinarily high packing fraction. The self-correlation functions measured using quasielastic neutron scattering clearly show the slowing down of microscopic dynamics with an increase in packing fraction. The self-diffusivity in liquid Ni60Nb34.8Sn5.2 decreases by about 2 orders of magnitude within a temperature range of 360 K. For these highly fragile systems, the critical packing fraction obtained form the analysis of incoherent data is in excellent agreement with the prediction made by mode-coupling theory. Our results provide the first experimentally observed value for the critical packing fraction in glass-forming metallic liquids.     

Observation of a superfluid phase in solid helium

Evidence of a superfluid liquid phase present in polycrystalline helium at a temperature of 0.2 K and a pressure of 51 bar has been obtained by means of inelastic neutron scattering. The superfluid component is absent at a temperature of 0.6 K and the same pressure. Thus, a “solid helium-superfluid helium” phase transition has been discovered. The sample of solid helium in a porous medium (silica aerogel) has been prepared with the use of a capillary blocking technique. The shape of the structure factor of the superfluid phase indicates the presence of clusters or the effects of a restricted geometry. The results may be used to explain the nonclassical rotational inertia phenomenon in solid helium (often referred to as supersolidity, Nature, 2004).     

The effect of magnetic fields on the electrodeposition of iron

The effect of a uniform magnetic field with flux density up to 1 T on the electrodeposition of Fe from sulphate electrolyte has been investigated under different field configurations relative to the electrode surface. Voltammetric and chronoamperometric experiments have been carried out coupled with an electrochemical quartz crystal microbalance for in situ mass change measurements. The structure and morphology of the deposited films were determined by scanning electron microscopy, atomic force microscopy and X-ray diffraction measurements. Results show that, when the magnetic field is applied parallel to the electrode surface, the limiting current density and the deposition rate are increased due to the magnetohydrodynamic effect. The nucleation process is also affected in parallel configuration; the current density of the maximum on the chronoamperograms is decreased, and an additional nucleation step might be observed. This effect is attributed to the hydrodynamic response of the electrochemical system. No significant influence on the electrochemical reaction was observed when a magnetic field was applied perpendicular to the electrode. But in this configuration, the morphology of deposited layers is changed by the magnetic field. The morphology changes are discussed. No effect of the magnetic field on the crystallographic structure was observed.     

Dynamic Lone Pair Expression as Chemical Bonding Origin of Giant Phonon Anharmonicity in Thermoelectric InTe

Loosely bonded (“rattling”) atoms with s² lone pair electrons are usually associated with strong anharmonicity and unexpectedly low thermal conductivity, yet their detailed correlation remains largely unknown. Here we resolve this correlation in thermoelectric InTe by combining chemical bonding analysis, inelastic X-ray and neutron scattering, and first principles phonon calculations. We successfully probe soft low-lying transverse phonons dominated by large In¹⁺ z-axis motions, and their giant anharmonicity. We show that the highly anharmonic phonons arise from the dynamic lone pair expression with unstable occupied antibonding states induced by the covalency between delocalized In¹⁺ 5s² lone pair electrons and Te 5p states. This work pinpoints the microscopic origin of strong anharmonicity driven by rattling atoms with stereochemical lone pair activity, important for designing efficient materials for thermoelectric energy conversion.