Partial-wave analysis of backwardly produced three-pion systems in K−p interactions at 4.2 GeV/c

We report on the results of a partial-wave analysis of the 3π system produced by baryon exchange in the reaction K^?p→Σ^?π⁺π⁺π^? at 4.2 GeV/c. We confirm the existence of an enhancement in the 1⁺S(?π) wave as previously established from a Dalitz plot analysis of the same data. The phase variation of this wave is found to be consistent with that expected for a resonance and thus the enhancement is identified with A₁ production. No clear signal for this state is found in either the reaction K^?p→Σ⁺π⁺π⁺π^?π^? or K^?p→Λπ⁺π^?π⁰. We also find production via baryon exchange of the A₂ in all three reactions and the ω and $\text{ω}{}^1$ (1975) in the third reaction.     

Ultrasonic pulsed Doppler transoesophageal measurement of aortic haemodynamics in humans.

Centreline blood velocity and exterior wall motion were measured in the descending aorta of humans using an oesophageal probe, a pulsed ultrasound Doppler velocity meter and an ultrasonic echo tracking system. The development of a method for easily measuring haemodynamics in the thoracic region using an oesophageal probe will provide an essentially non-invasive method for the assessment of cardiac function and the nature of blood vessels in that region. Detailed anatomical studies of the thorax were conducted by cross-sectioning of the thorax of a cadaver. Blood velocity waveforms were recorded from the descending aorta both during rest and exercise. In one volunteer, the peak centreline velocity increased from a resting value of approximately 30 cm s-1 to an exercise value of approximately 50 cm s-1. Vessel diameter waveforms similar to those for pressure were also recorded showing diameter changes of 1.8 mm. The accuracy and resolution of the technique would be improved by multicrystal probes and multigate ultrasonic flowmeters allowing for accurate calculation of the Doppler angle, imaging of vascular flow regions, and measurement of pulse wave velocity.     

Least squares cross-validation for the kernel deconvolution density estimatorValidation croisée pour l'estimateur à noyau de la déconvolution d'une densité

Assume we have i.i.d. replications from the corrupted random variable Y=X+ε, where X and ε are independent. We propose a data-driven bandwidth based on cross-validation ideas, for the kernel deconvolution estimator of the density of X. The proposed method is shown to be asymptotically optimal. To cite this article: É. Youndjé, M.T. Wells, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 509–513.     

Ionization of atoms by the spatial gradient of the pondermotive potential in a focused laser beam

Ionization of atoms by the spatial gradient of the pondermotive potential in a focused laser beam is investigated. Rydberg ions, formed during the interaction of noble gas atoms with an intense laser pulse, are used to probe the gradient field. Rydberg ion species with higher ionization potentials are produced at locations where the gradient field is largest. The measured Rydberg ion yields differ dramatically from estimates that ignore gradient-field ionization, but are in good agreement with predictions that include the effect.     

On the twist-bend nematic phase formed directly from the isotropic phase

The intriguing twist-bend nematic (N_TB) phase is formed, primarily, by liquid crystal dimers having odd spacers. Typically, the phase is preceded by a nematic (N) phase via a weak first-order transition. Our aim is to obtain dimers where the N_TB phase is formed directly from the isotropic (I) phase via a strong first-order phase transition. The analogy between such behaviour and that of the smectic A (SmA)–N–I sequence suggests that this new dimer will require a short spacer. This expectation is consistent with the prediction of a molecular field theory, since the decrease in the spacer length results in an increase in the molecular curvature. A vector of odd dimers based on benzoyloxybenzylidene mesogenic groups with terminal ethoxy groups has been synthesised with spacers composed of odd numbers of methylene groups. Spacers having 5, 7, 9 and 11 methylene groups are found to possess the conventional phase sequence N_TB–N–I; surprisingly, for the propane spacer, the N_TB phase is formed directly from the I phase. The properties of these dimers have been studied with care to ensure that the identification of the N_TB phase is reliable.     

Capillary electrophoresis determination of diatrizoic acid and its impurities in diatrizoate radiopaque solutions

A capillary electrophoresis method has been developed for the separation and determination of diatrizoic acid (DTZA) and its four mono- and diiodo degradation products (2-iodo,4-iodo, 2,4-diiodo, and 2,6-diiodo-3,5-diacetamidobenzoic acid) in radio-paque solution for injection (RSI). DTZA and its degradants were assayed in suitable dilutions without pretreatment. Optimum conditions included the use of low-pressure sample injection (6 s), sample and standard solutions with a molarity less than that of the separation buffer, and adjustment of the buffer molarity to obtain a current of 50 A at a constant 15kV separation voltage. After each six runs or less, the inlet and outlet buffer were replaced with more buffer from the same batch. When the method was applied to a sample of SI levels of 5–10 mg/ml were found for each of the mono and diiodo impurities. The optimum method showed a precision (peak area measurement) in the range 1.7–7.2% RSD, depending on the concentration. A linear correlation coefficient of 0.997 was obtained over a DTZA concentration range of 5–60 mg/mL.     

Suitability of N,O-bis(trimethylsilyl)trifluoroacetamide and N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide as derivatization reagents for the determination of the estrogens estrone and 17alpha-ethinylestradiol by gas chromatography-mass spectrometry

This paper describes apreviously unreported problem with the use of N,O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA) and N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA) to derivatise the natural hormone estrone (E1) and the synthetic estrogen 17alpha-ethinylestradiol (EE2). The resulting trimethylsilyl (TMS) and t-butyldimethylsilyl (TBS) derivatives of EE2 were partially converted to their respective El derivatives. Therefore, these reagents may not be suitable for simultaneous determination of estrogens in environmental samples, which raises questions about the reliability of results from some earlier studies.     

Investigating the Influence of (Deoxy)fluorination on the Lipophilicity of Non‐UV‐Active Fluorinated Alkanols and Carbohydrates by a New log P Determination Method

Property tuning by fluorination is very effective for a number of purposes, and currently increasingly investigated for aliphatic compounds. An important application is lipophilicity (log P) modulation. However, the determination of log P is cumbersome for non‐UV‐active compounds. A new variation of the shake‐flask log P determination method is presented, enabling the measurement of log P for fluorinated compounds with or without UV activity regardless of whether they are hydrophilic or lipophilic. No calibration curves or measurements of compound masses/aliquot volumes are required. With this method, the influence of fluorination on the lipophilicity of fluorinated aliphatic alcohols was determined, and the log P values of fluorinated carbohydrates were measured. Interesting trends and changes, for example, for the dependence on relative stereochemistry, are reported.