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1.
Y. Yaci A. Kornowski W. Schnabel 《Journal of polymer science. Part A, Polymer chemistry》1992,30(9):1987-1991
The polymerization of n-butyl vinyl ether (BVE), cyclohexene oxide (CHO) and 3,4-epoxycyclohexyl(methyl)-3′,4′-epoxycyclohexane carboxylate (EEC) was initiated upon UV irradiation (λinc > 300 nm) of dichloromethane solutions containing N-ethoxy-2-methylpyridinium ( V ), N-ethoxy-4-phenyl-pyridinium ( VI ) or N-ethoxy-isoquinolinium hexafluorophosphate ( VII ). Whereas the bifunctional EEC was converted into an insoluble gel, BVE and CHO formed polymers of molar mass: Mw = 2 X 104?2 X 105 (PCHO) and Mw ≈ 2 X 104 (PBVE). Protons are formed with a rather high quantum yield [ø(H+) = 0.48 on irradiating VII in dichloromethane; titration with sodium p-nitrophenolate] and it is, therefore, assumed that the polymerization is initiated by photochemically generated protons. © 1992 John Wiley & Sons, Inc. 相似文献
2.
Poly(phenylisopropenylketone (PPIK) and copolymers of PIK and methylmethacrylate (MMA) or styrene (St) were irradiated in benzene solution at 30° with 313 nm light (stationary irradiations) or with 347 nm light (flash photolysis experiments). Homo PPIK undergoes main chain degradation (β-scission) with ø(S) ≈ 0.05. The quantum yield for α-scission is ø(α) = 0.3. For copolymers of MMA and PIK (1 to 15 mol%), ø(S) is 0.04 independent of the copolymer composition. With copolymers of St and PIK, ø(S) was found to increase with decreasing PIK content and to approach 0.15 for very small PIK contents. The flash photolysis experiments showed: (a) the carbonyl triplet decay rate constant kT(6 × 106 sec?1) for CP-MMA-PIK samples is independent of copolymer composition but is lower than for homo PPIK (1 × 107 sec?1). In CP-St-PIK samples kT decreases with decreasing PIK content [from 8 × 106 sec?1 (12 mol% PIK) to 3 × 106 sec?1 (1 mol% PIK)]; (b) the transient spectra of triplet decay products indicate the formation of benzoyl radicals in the cases of PPIK and CP-MMA-PIK, and the formation of various different species in the case of CP-St-PIK.The results are consistent with the following concept. In homo PPIK and CP-MMA-PIK, α-scission (Norrish type I) is the dominant chemical route of triplet deactivation. In CP-St-PIK, however, type II processes become more and more important as the PIK content decreases. 相似文献
3.
Clostridium botulinum type E is a cold-tolerant, neurotoxigenic, endospore-forming organism, primarily associated with aquatic environments. High pressure thermal (HPT) processing presents a promising tool to enhance food safety and stability. The effect of fat on HPT inactivation of C. botulinum type E spores was investigated using an emulsion model system. The distribution of spores in oil-in-water (O/W) emulsions and their HPT (300–750?MPa, 45–75?°C, 10?min) inactivation was determined as a function of emulsion fat content (30–70% (v/v) soybean oil in buffer). Approximately 26% and 74% of the spores were located at the oil–buffer interface and the continuous phase, respectively. Spore inactivation in emulsion systems decreased with increasing oil contents, which suggests that the fat content of food plays an important role in the protection of C. botulinum type E endospores against HPT treatments. These results can be helpful for future safety considerations. 相似文献
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Richard H. Byrd Cornelius L. Dert Alexander H. G. Rinnooy Kan Robert B. Schnabel 《Mathematical Programming》1990,46(1-3):1-29
The global optimization problem, finding the lowest minimizer of a nonlinear function of several variables that has multiple local minimizers, appears well suited to concurrent computation. This paper presents a new parallel algorithm for the global optimization problem. The algorithm is a stochastic method related to the multi-level single-linkage methods of Rinnooy Kan and Timmer for sequential computers. Concurrency is achieved by partitioning the work of each of the three main parts of the algorithm, sampling, local minimization start point selection, and multiple local minimizations, among the processors. This parallelism is of a coarse grain type and is especially well suited to a local memory multiprocessing environment. The paper presents test results of a distributed implementation of this algorithm on a local area network of computer workstations. It also summarizes the theoretical properties of the algorithm.Research supported by AFOSR grant AFOSR-85-0251, ARO contract DAAG 29-84-K-0140, NSF grant DCR-8403483, and NSF cooperative agreement DCR-8420944. 相似文献
7.
DiGuglielmo J Samblowski A Hage B Pineda C Eisert J Schnabel R 《Physical review letters》2011,107(24):240503
Among the possibly most intriguing aspects of quantum entanglement is that it comes in free and bound instances. The existence of bound entangled states certifies an intrinsic irreversibility of entanglement in nature and suggests a connection with thermodynamics. In this Letter, we present a first unconditional, continuous-variable preparation and detection of a bound entangled state of light. We use convex optimization to identify regimes rendering its bound character well certifiable, and continuously produce a distributed bound entangled state with an extraordinary and unprecedented significance of more than 10 standard deviations away from both separability and distillability. Our results show that the approach chosen allows for the efficient and precise preparation of multimode entangled states of light with various applications in quantum information, quantum state engineering, and high precision metrology. 相似文献
8.
R. Schnabel M. Schultz-Johanning M. Kock 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):267-269
Radiative lifetimes of 19 selected W II levels with energies between 36 000 cm-1 and 55 000 cm-1 have been measured with the time-resolved laser-induced fluorescence technique. The ions are generated in a hollow cathode
discharge and stored in a linear Paul trap. Selected states are populated with tunable dye laser pulses and the subsequent
fluorescence is measured by means of a 5 Gigasample transient digitizer and a fast photodetector with a risetime of 700 ps.
By taking into account both the temporal profile of the laser pulses and the separately measured response function of the
system, the lifetime can be determined from the full decay curve. A refined evaluation procedure, taking into account saturation
effects in the signals, reduces the uncertainty in our data to around 1%.
Received: 30 July 1998 / Revised: 18 August 1998 相似文献
9.
Four-wave mixing in semiconductor laser amplifiers enables various applications in photonic switching including wavelength conversion, space and time switching, optical phase conjugation, and demultiplexing. Switching times faster than 1 ps are possible. 相似文献
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