Stereoelectronic control of the rate of ring opening in azidofurans

5-Azido-2-furyl alkyl ketones are converted into nitrogen and 4,5-dioxo-2-alkenenitriles in a reaction whose facility depends on the nature of the alkyl group.     

Interface broadening during ion plating

Radiation damaged fluorite single crystals iso-thermally annealed showed an oscillating structure of the intensity of a diffracted neutron beam. This is in accord with previous report on crystalline cobaltic compound examined for reconstitution of parent complex ions from recoil hot atoms and for annealing of radiation damage by neutron diffraction. The oscillation phenomenon already found by radiochemical means in various solids irrespectively of their chemical constitution combined by a pure physical method as the neutron diffraction, greatly supports a hypothesis of a spatial temporal oscillatory diffusion of defects in isothermal annealing of radiation damaged crystalline lattice.     

Scope of the directed dihydroxylation: application to cyclic homoallylic alcohols and trihaloacetamides

The synthesis and directed dihydroxylation of a range of cyclic alkenes was investigated. Both homoallylic alcohols and homoallylic trihaloacetamides were found to be efficient directing groups, giving rise to good to excellent levels of remote asymmetric induction with OsO4-TMEDA. Interestingly, in all cases examined, trifluoroacetamides were found to be superior to trichloroacetamides as directing groups and an argument is presented which rationalises this observation.     

Scale size of magnetic turbulence in tokamaks probed with 30-MeV electrons

Measurements of synchrotron radiation emitted by 30-MeV runaway electrons in the TEXTOR-94 tokamak show that the runaway population decays after switching on neutral beam injection (NBI). The decay starts only with a significant delay, which decreases with increasing NBI heating power. This delay provides direct evidence of the energy dependence of runaway confinement, which is expected if magnetic modes govern the loss of runaways. Application of the theory by Mynick and Strachan [Phys. Fluids 24, 695 (1981)] yields estimates for the "mode width" (delta) of magnetic perturbations: delta<0.5 cm in Ohmic discharges, increasing to delta = 4.4 cm for 0. 6 MW NBI.     

Diffusion approximations to cascade mixing

In two recent studies^{1, 2} of cascade mixing, the process in which energetic ion bombardment can redistribute the atomic components of a multielemental target via recoil processes, a diffusion approximation has been assumed, apparently with signif-icantly different results². It is the purpose of this communication to reveal the close similarity of the two existing treatments and to indicate some important modifications and extensions.     

微囊藻毒素-LR的特征红外光谱

利用傅里叶变换红外(FTIR)光谱仪研究了微囊藻毒素-LR在扫描范围4 000～600 cm-1的红外吸收光谱图,微囊藻毒素-LR分子构成中的主要官能团,如带有单一取代基的苯环、胍基、γ-羧基等特征红外吸收带在谱图上均得到了确认。     

Mapping Aldehyde Dehydrogenase 1A1 Activity using an [18F]Substrate-Based Approach

Aldehyde dehydrogenases (ALDHs) catalyze the oxidation of aldehydes to carboxylic acids. Elevated ALDH expression in human cancers is linked to metastases and poor overall survival. Despite ALDH being a poor prognostic factor, the non-invasive assessment of ALDH activity in vivo has not been possible due to a lack of sensitive and translational imaging agents. Presented in this report are the synthesis and biological evaluation of ALDH1A1-selective chemical probes composed of an aromatic aldehyde derived from N,N-diethylamino benzaldehyde (DEAB) linked to a fluorinated pyridine ring either via an amide or amine linkage. Of the focused library of compounds evaluated, N-ethyl-6-(fluoro)-N-(4-formylbenzyl)nicotinamide 4 b was found to have excellent affinity and isozyme selectivity for ALDH1A1 in vitro. Following ¹⁸F-fluorination, [¹⁸F] 4 b was taken up by colorectal tumor cells and trapped through the conversion to its ¹⁸F-labeled carboxylate product under the action of ALDH. In vivo positron emission tomography revealed high uptake of [¹⁸F] 4 b in the lungs and liver, with radioactivity cleared through the urinary tract. Oxidation of [¹⁸F] 4 b , however, was observed in vivo, which may limit the tissue penetration of this first-in-class radiotracer.