The MLLTRAP at the Maier-Leibnitz-Laboratory (Garching) is a new Penning trap facility designed to combine several novel technologies
to decelerate, charge breed, cool, bunch and purify the reaction products and perform high-accuracy nuclear and atomic mass
measurements. It is now in the commissioning phase, achieving a mass-resolving power of about 105 in the purification trap for stable ions. 相似文献
Changes in both blood flow and blood oxygenation determine the functional MRI (fMRI) signal. In the present study factors responsible for blood oxygenation (e.g., FiO(2)) were held constant so that changes in pixel count would above all reflect changes in regional cerebral blood flow (rCBF). Continuous positive airway pressure (CPAP) breathing at 12 cm H(2)O, which was previously shown to influence rCBF, was applied in human volunteers (n = 19) to investigate the sensitivity of fMRI for changes in rCBF caused by increased mean airway pressure. Increasing the mean airway pressure decreased the pixel count in the primary visual cortex (median (range)): baseline: 219 (58-425) pixels vs. CPAP (12 cm H(2)O): 92 (0-262) pixels). These findings indicate that fMRI is sensitive to detect a reduced rCBF-response in the primary visual cortex. The underlying mechanism is likely to be a reduced basal rCBF due to constriction and/or compression of postcapillary venoles during CPAP breathing. These findings are important for interpreting fMRI results in awake and in artificially respirated patients, in whom positive airway pressure is used to improve pulmonary function during the diagnostic procedure. 相似文献
Titanium dioxide is one of the most intensely studied oxides due to its interesting electrochemical and photocatalytic properties and it is widely applied, for example in photocatalysis, electrochemical energy storage, in white pigments, as support in catalysis, etc. Common synthesis methods of titanium dioxide typically require a high temperature step to crystallize the amorphous material into one of the polymorphs of titania, e.g. anatase, brookite and rutile, thus resulting in larger particles and mostly non-porous materials. Only recently, low temperature solution-based protocols gave access to crystalline titania with higher degree of control over the formed polymorph and its intra- or interparticle porosity. The present work critically reviews the formation of crystalline nanoscale titania particles via solution-based approaches without thermal treatment, with special focus on the resulting polymorphs, crystal morphology, surface area, and particle dimensions. Special emphasis is given to sol-gel processes via glycolated precursor molecules as well as the miniemulsion technique. The functional properties of these materials and the differences to chemically identical, non-porous materials are illustrated using heterogeneous catalysis and electrochemical energy storage (battery materials) as example. 相似文献
Enantioselective conjugate reduction of a wide range of α,β‐unsaturated carboxylic esters was achieved using chiral Ir N,P complexes as hydrogenation catalysts. Depending on the substitution pattern of the substrate, different ligands perform best. α,β‐Unsaturated carboxylic esters substituted at the α position are less problematic substrates than originally anticipated and in some cases α‐substituted substrates actually reacted with higher enantioselectivity than their β‐substituted analogues. The resulting saturated esters with a stereogenic center in the α or β position were obtained in high enantiomeric purity. 相似文献
Anesthesia for diagnostic procedures, e.g., MRI measurements, has increasingly used sevoflurane and nitrous oxide in recent years. Sevoflurane and nitrous oxide are known cerebrovasodilatators, however, which potentially interferes with MRI examination of cerebral hemodynamics. To compare the effects of relevant equianesthetic concentrations (0.4 MAC) of both drugs on regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) we used contrast-enhanced magnetic resonance imaging (MRI) perfusion measurement, which has the advantage of providing regional anatomic resolution.
Sevoflurane increased rCBF more than did nitrous oxide in all regions except in parietal and frontal gray matter. Nitrous oxide, by contrast, increased rCBV in most of the gray matter regions more than did sevoflurane. In summary we show that, in contrast to nitrous oxide, sevoflurane supratentorially reversed the anterior-posterior gradient in rCBF and typically redistributed rCBF to infratentorial gray matter. In contrast, nitrous oxide increased rCBV more than did sevoflurane. Both inhalational anesthetics had a drug-specific influence on cerebral hemodynamics, which is of importance when interpreting MRI studies of cerebral hemodynamics in anesthetized patients. 相似文献
The title compound, C16H26O2, (I), prepared by oxidation of (1R*,11R*)‐12‐hydroxybicyclo[9.4.1]hexadecan‐16‐one using pyridinium dichromate, has a trans configuration of the two fused rings and represents an interesting precursor for the synthesis of macrocyclic structures. 相似文献
The aim of this note is to give short algebraic proofs of theorems of Handelman, Pólya and Schmüdgen concerning the algebraic
structure of polynomials being positive on certain subsets of ℝn. The main ingredient of the proofs is the representation theorem of Kadison–Dubois. The proof of the latter is elementary
and algebraic but tricky.
Received: 6 February 1999 / Revised version: 28 August 2000 相似文献
Mean lives and limits of lifetimes have been determined for some ten mostly yrast states in70Se, by means of the recoil distance Doppler shift technique. The states were excited in the reaction40Ca(36Ar,α2p) at 115 MeV resp. the reaction58Ni(14N,pn) at 39 MeV beam energy. The systematic decrease ofB(E2) values along the the ground band transitions indicates a band crossing consistent with theγ-ray energies. Effects of continuum feeding times in both reactions are being discussed. The lifetimes of the lowest three yrast transitions in72Se have been remeasured by means of the reactions40Ca(36Ar,4p) and60Ni(14N,pn). 相似文献