Pressure Transients for Boron-Potassium Nitrate Igniters in Inert, Vented Chambers

Equations which will describe the pressure-time curves for the ignition of cylindrical, boron-potassium nitrate, igniter pellets in vented, inert chambers are derived on the assumption that the burning rate is independent of pressure. This assumption is justified on the basis of closed chamber experiments. Experimental firings were conducted over a considerable range of igniter weights and nozzle throat sizes. Smooth, reproducible pressure- time histories were obtained which showed excellent agreement with the analytically predicted curves

Kinetic-energy release in Coulomb explosion of metastable C3H52+

C3H52+, formed by electron impact ionization of propane, undergoes metastable decay into C2H2++CH3+. We have monitored this reaction in a magnetic mass spectrometer of reversed geometry that is equipped with two electric sectors (BEE geometry). Three different techniques were applied to identify the fragment ions and determine the kinetic-energy release (KER) of spontaneous Coulomb explosion of C3H52+ in the second and third field free regions of the mass spectrometer. The KER distribution is very narrow, with a width of about 3% [root-mean square standard deviation]. An average KER of 4.58+/-0.15 eV is derived from the distribution. High level ab initio quantum-chemical calculations of the structure and energetics of C3H52+ are reported. The activation barrier of the reverse reaction, CH3++C2H2+ (vinylidene), is computed. The value closely agrees with the experimental average KER, thus indicating that essentially all energy available in the reaction is partitioned into kinetic energy. (C) 2003 American Institute of Physics

Ionization of Ammonia Nanoices With Adsorbed Methanol Molecules

Large ammonia clusters represent a model system of ices which are omnipresent throughout the space. The interaction of ammonia ices with other hydrogen-boding molecules such as methanol or water and their behavior upon an ionization are thus relevant in the astrochemical context. In this study, ammonia clusters (NH3)N with the mean size N ~230 were prepared in molecular beams and passed through a pickup cell in which methanol molecules were adsorbed. At the highest exploited pickup pressures, the average composition of (NH3)N(CH3OH)M clusters was estimated to be N:M ~210:10. On the other hand, the electron ionization of these clusters yielded about 75% of methanol-containing fragments (NH3)n(CH3OH)mH+ compared to 25% contribution of pure ammonia (NH3)nH+ ions. Based on this substantial disproportion, we propose the following ionization mechanism: The prevailing ammonia is ionized in most cases, resulting in NH+4 core solvated most likely with four ammonia molecules, yielding the well-known "magic number" structure (NH3)4NH+4 . The methanol molecules exhibit strong propensity for sticking to the fragment ion. We have also considered mechanisms of intracluster reactions. In most cases, proton transfer between ammonia units take place. The theoretical calculations suggested the proton transfer either from the methyl group or from the hydroxyl group of the ionized methanol molecule to ammonia to be the energetically open channels. However, the experiments with selectively deuterated methanols did not show any evidence for the D+ transfer from the CD3 group. The proton transfer from the hydroxyl group could not be excluded entirely nor confirmed unambiguously by the experiment.Comment: J Phys Che

Arbeitszeit - eine wichtige Dimension für die Lebenslaufperspektive?

Die Debatte zur Lebensverlaufspolitik im Kontext Arbeit ist insbesondere in der Diskussion um den demografischen Wandel, die Vereinbarkeit von beruflichen und außerberuflichen Anforderungen während der verschiedenen Lebensphasen sowie die bessere Nutzung und den längerfristigen Erhalt des Beschäftigungspotenzials verstärkt aufgekommen. Im Zusammenhang mit der Ausdifferenzierung und Flexibilisierung der Beschäftigungsverhältnisse, die neben dem Erwerbsverlauf auch die weiteren Dimensionen des Lebenslaufs wie Aus- und Weiterbildung, Familie, Gesundheit und gesellschaftliches Engagement betreffen, steigt die Bedeutung der Gestaltung von Arbeitszeit als einem wichtigen Instrument zur Organisation, Koordination und Synchronisation im Alltag sowie im Lebenslauf. Der Arbeitszeitgestaltung kommt bei der Bewältigung von Risiken und Unsicherheiten aufgrund des fortschreitenden Strukturwandels der Erwerbsarbeit und der Erwerbsverläufe eine wichtige Funktion zu. Das vorliegende Papier gibt daher einen Überblick über das Forschungsthema Arbeitszeit in der Lebenslaufperspektive.The debate on the life course policy concerning employment intensified particularly with regard to the debate on demographic change, the balance of job-related and private demands during the different phases of life as well as with the improved utilisation and the long-term preservation of manpower reserves (employability). In connection with the differentiation and the flexibilisation of employment which also affects the course of one's employment in addition to all the other dimensions of a person's life like vocational training and further education, family, health, and social commitment, there is a growing importance of the organisation of working time as a fundamental instrument for the organisation, coordination, and synchronisation in both everyday life and life course. The organisation of working time is a matter of great significance referring to coping with the risks and uncertainties due to proceeding structural change of the gainful occupation and the course of one's employment. This paper gives an overview of the research on working time pertaining to the perspective of life course

Development of multisensory spatial integration and perception in humans

Previous studies have shown that adults respond faster and more reliably to bimodal compared to unimodal localization cues. The current study investigated for the first time the development of audiovisual (A‐V) integration in spatial localization behavior in infants between 1 and 10 months of age. We observed infants’ head and eye movements in response to auditory, visual, or both kinds of stimuli presented either 25° or 45° to the right or left of midline. Infants under 8 months of age intermittently showed response latencies significantly faster toward audiovisual targets than toward either auditory or visual targets alone They did so, however, without exhibiting a reliable violation of the Race Model, suggesting that probability summation alone could explain the faster bimodal response. In contrast, infants between 8 and 10 months of age exhibited bimodal response latencies significantly faster than unimodal latencies for both eccentricity conditions and their latencies violated the Race Model at 25° eccentricity. In addition to this main finding, we found age‐dependent eccentricity and modality effects on response latencies. Together, these findings suggest that audiovisual integration emerges late in the first year of life and are consistent with neurophysiological findings from multisensory sites in the superior colliculus of infant monkeys showing that multisensory enhancement of responsiveness is not present at birth but emerges later in life

Resonant electron attachment to mixed hydrogen/oxygen and deuterium/oxygen clusters

Low energy electron attachment to mixed (H$_2$)$_x$/(O$_2$)$_y$ clusters and their deuterated analogues has been investigated for the first time. These experiments were carried out using liquid helium nanodroplets to form the clusters, and the effect of the added electron was then monitored via mass spectrometry. There are some important differences between electron attachment to the pure clusters and to the mixed clusters. A particularly notable feature is the formation of HO$_2$$^{-}$ and H$_2$O$^{-}$ ions from an electron-induced chemical reaction between the two dopants. The chemistry leading to these anions appears to be driven by electron resonances associated with H$_2$ rather than O$_2$. The electron resonances for H$_2$ can lead to dissociative electron attachment (DEA), just as for the free H$_2$ molecule. However, there is evidence that the resonance in H$_2$ can also lead to rapid electron transfer to O$_2$, which then induces DEA of the O$_2$. This kind of excitation transfer has not, as far as we are aware, been reported previouslyComment: 18 pages, 4 figure