Ion-induced nucleation: the importance of chemistry

Experiments have shown that ions can substantially increase vapor-to-liquid nucleation rates. However, interpretation of these experiments is complicated by ambiguities arising from the manner in which the ions are produced. Several studies have concluded that water has a general preference for anions over cations. We show that specification of the ion's sign alone is insufficient to provide an understanding of the aqueous ionic cluster thermodynamics and that classical ion-induced nucleation theory does not treat the cluster physics properly to describe ion-induced nucleation accurately.     

Editorial: Past,present and future of the combinatorial chemistry in Spain

Molecular Diversity -     

Combustion chemistry probed by synchrotron VUV photoionization mass spectrometry

Combustion is directly related to energy conversion and the environment. Gas-phase chemical reactions such as thermal decomposition, oxidation and recombination play a critical role in combustion processes. Here we review six applications of synchrotron vacuum-ultraviolet (VUV) photoionization mass spectrometry (PIMS) in fundamental studies of combustion chemistry. These applications range from the use of flow reactors to probe elementary reaction kinetics, studies of pyrolysis in plug-flow reactors and oxidation in jet-stirred reactors, studies of spatial evolution of species concentrations in premixed and non-premixed flames, product distributions in pyrolysis of biomass, and analysis of polycyclic aromatic hydrocarbon (PAH) formation. These experiments provide valuable data for the development and validation of detailed chemical kinetic models. Furthermore, some additional potential applications are proposed.     

Enhanced anisotropy in Paratellurite for inhomogeneous waves and its possible importance in the future development of acousto-optic devices

The anisotropic feature of most crystals, involves a direction dependent wave velocity for each of the possible modes. Paratellurite (Tellurium dioxide) is extraordinary because, for one of the propagation modes, i.e. the quasi shear horizontal (QSH) mode, the anisotropy is exceptional. This results, on the one hand in a very strong directional dependent sound velocity and on the other hand, in a low wave velocity in certain directions, resulting in a high figure of merit for the acousto-optical interaction. In the case of inhomogeneous waves, the slowness surfaces change their shape and magnitude, for all crystals. However, for paratellurite, this effect is again extraordinary. As soon as a relatively small inhomogeneity is considered, the sound velocity for the QSH mode becomes really exceptionally anisotropic, resulting in a slowness surface that is almost spherical, covered by pins. The velocity corresponding to those 'pins', is much lower than in the case of homogeneous plane waves, which is very promising for the future development of acousto-optic cells involving an even higher figure of merit.     

Spectroscopic techniques in medicine: The future of diagnostics

Spectroscopic techniques have been finding increasing applications in the field of biomedicine especially in the field of disease diagnosis and monitoring in spite of the rapid emergence of several molecular biology based techniques. The significance of spectroscopy techniques and the possibility of using some of the underutilized regions of the electromagnetic radiations are discussed in this review. While previous reviews have already dealt with the potential of Fourier transform infrared spectroscopy-based (FTIR) techniques for clinical applications, the present review addresses the lacunae of the techniques along with its future trends that may make it a technique routinely applied in clinical settings.     

The importance of the reaction volume in hadronic collisions

The pair production in the thermodynamic model is shown to depend sensitively on the (hadronic) reaction volume. Strangeness production in nucleus-nucleus collisions is treated as an example.     

Ion-enhanced gas-surface chemistry: The influence of the mass of the incident ion

There are many examples of situations in which a gas-surface reaction rate is increased when the surface is simultaneously subjected to energetic particle bombardment. There are several possible mechanisms which could be involved in this radiation-enhanced gas-surface chemistry. In this study, the reaction rate of silicon, as determined from the etch yield, is measured during irradiation of the Si surface with 1 keV He⁺, Ne⁺, and Ar⁺ ions while the surface is simultaneously subjected to fluxes of XeF₂ or Cl₂ molecules. Etch yields as high as 25 Si atoms/ion are observed for XeF₂ and Ar⁺ on Si. A discussion is presented of the extent to which these results clarify the mechanisms responsible for ion-enhanced gas-surface chemistry.     

The importance of the voice in male-to-female transsexualism.

Transsexuality is a complex, permanent transposition involving a paradoxical feeling of belonging to the opposite sex. Furthermore, in the case of male-to-female transsexuals, the unchanged male voice, which is at odds with the female outward appearance, poses a serious obstacle to full social integration of the woman. One way of permanently raising the fundamental frequency, requiring little effort, is modified cricothyroidopexy via miniplates, which has been used in our hospital since 1993 following a technique developed by Isshiki (thyroplasty type IV). Until now, this operation has been performed on 67 female patients. To record the anatomical-morphological and functional data, preoperatively, post-operatively, and a year after the operation, a detailed voice diagnosis was made, laryngoscopy was carried out, X-rays were taken, and computer-assisted tomography was used to examine the larynx. Thus far, the functional results have been good. On average, the fundamental frequency has been raised by about one fourth. Whereas none of the female patients had a female-speaking voice before the operation, after the operation, about 30% of the patients' voices were in the female range, and 32% had at least a neutral-sounding voice.     

Many-body localization in disorder-free systems: The importance of finite-size constraints

Recently it has been suggested that many-body localization (MBL) can occur in translation-invariant systems, and candidate 1D models have been proposed. We find that such models, in contrast to MBL systems with quenched disorder, typically exhibit much more severe finite-size effects due to the presence of two or more vastly different energy scales. In a finite system, this can artificially split the density of states (DOS) into bands separated by large gaps. We argue for such models to faithfully represent the thermodynamic limit behavior, the ratio of relevant coupling must exceed a certain system-size depedent cutoff, chosen such that various bands in the DOS overlap one another. Setting the parameters this way to minimize finite-size effects, we study several translation-invariant MBL candidate models using exact diagonalization. Based on diagnostics including entanglement and local observables, we observe thermal (ergodic), rather than MBL-like behavior. Our results suggest that MBL in translation-invariant systems with two or more very different energy scales is less robust than perturbative arguments suggest, possibly pointing to the importance of non-perturbative effects which induce delocalization in the thermodynamic limit.     

The surface chemistry of catalysis: new challenges ahead

Surface scientists have over the last few decades greatly advanced the atomic level understanding of the surface chemical reactions associated with heterogeneous catalysis. Nonetheless, many fundamental questions still remain unanswered. In this review, a critical analysis of the state of the art of this field is provided, and a number of future research directions are suggested.     

The importance of selection rate in the evolution of cooperation

How cooperation emerges in human societies is still a puzzle. Evolutionary game theory has been the standard framework to address this issue. In most models, every individual plays with all others, and then reproduces and dies according to what she earns. This amounts to assuming that selection takes place at a slow pace with respect to the interaction time scale. We show that, quite generally, if selection speeds up, the evolution outcome changes dramatically. Thus, in games such as Harmony, where cooperation is the only equilibrium and the only rational outcome, rapid selection leads to dominance of defectors. Similar non trivial phenomena arise in other binary games and even in more complicated settings such as the Ultimatum game. We conclude that the rate of selection is a key element to understand and model the emergence of cooperation, and one that has so far been overlooked.     

The future is noisy: the role of spatial fluctuations in genetic switching

A genetic switch may be realized by a certain operator sector on the DNA strand from which either genetic code, to the left or to the right of this operator sector, can be transcribed and the corresponding information processed. This switch is controlled by messenger molecules, i.e., they determine to which side the switch is flipped. Recently, it has been realized that noise plays an elementary role in genetic switching, and the effect of number fluctuations of the messenger molecules have been explored. Here we argue that the assumption of well stirredness taken in the previous models may not be sufficient to characterize the influence of noise: spatial fluctuations play a non-negligible part in cellular genetic switching processes.     

The ultrahigh-peak-power laser: present and future

19 to 10²⁰-W/cm² range. With some refinements and with superior energy storage materials, even higher peak power in the petawatt range should be possible from tabletop systems. In this paper we show the ultimate achievable power and intensity, as well as their applications in science and technology. Their applications cover a wide variety of fields, such as precision surgery, micromachining, coherent and incoherent X-ray generation, thermonuclear ignition, particle acceleration, and nonlinear quantum electrodynamics. Received: 5 May 1997/Revised version: 2 June 1997     

The importance of railway noise in France

A national survey on environmental nuisances due to all forms of transport was made in France during 1977. From among the data gathered, it is possible to extract results concerning the impact of nuisance due to railways, partly from results of questionnaires and partly from results of acoustical measurements. Interviews and measurements were made in several towns, at randomly selected dwellings. Rail and air transport noise nuisance impacts appeared to be of comparable importance, with that of road transport very much larger than either.     

JET: Preparing the future in fusion

JET (Joint European Torus) is the largest tokamak in the world and the only fusion facility able to operate with Tritium, the fusion fuel, and Beryllium, the ITER first wall material. JET also features the most complete remote handling equipment for invessel maintenance. As a multinational research center, JET provides logistic experience in preparing for operation of the global facility, tokamak ITER.Experiments on JET are focused on ITER-relevant studies, in particular on detailing the operational scenarios (EL My H-modes and advanced regimes), on enhancing the heating systems, on developing diagnostics for burning plasmas etc. Pioneering real-time control techniques have been implemented that maximize performance and minimize internal disturbances of JET plasmas. In helium plasmas, ion cyclotron heating (ICRH) created fast α-particles, mimicking their populations in future burning plasmas. The recent successful Trace Tritium campaign provided important new data on fuel transport. Current enhancements on JET include a new ITER-like ELM-resilient high power ICRH antenna (7 MW) and over twenty new diagnostics that will further extend the JET scientific capabilities and push the facility even closer to the ITER parameters.A special mention is given to the involvement of the fusion experts from Association EURATOM-IPP.CR, who have been actively participating in the collective use of JET facility for more than three years.     

Hyperfine interactions and nuclear probes in chemistry: The active interface

A symposium entitled “Hyperfine Interaction and Nuclear Probes in Chemistry” was held in conjunction with the 198 th. National Meeting of the American Chemical Society in Miami Beach, Florida, 12 and 13 September 1989. The four half-day sessions consisted of 15 invited and 4 contributed papers, and allowed numerous opportunities for spirited discussion and information exchange, especially at the informal luncheons and pre-dinner periods, and Miami Beach proved to be a most effective venue for these activities. In the pages to follow are collected a number of the scientific reports presented at this symposium; other contributions will be published elsewhere at the discretion of the author(s).     

不同燃烧状态飞火颗粒自由燃烧规律研究

飞火是开放空间中大尺度火灾非连续性蔓延的主要形式.本文通过不同热流下的木质飞火颗粒自由燃烧实验,揭示不同燃烧状态飞火颗粒的结构变形、质量损失及温度分布的变化规律.研究表明,颗粒结构变形受材料化学反应机制和热机械力作用共同影响;颗粒燃烧反应易造成热解气体的内部积聚,以致内压激增、诱发喷射或喷溅细小颗粒的现象;阴燃过程颗粒...