bluuebunny/crossref_metadata_2025 huggingface dataset:
Special issue on ‘Logical frameworks and metalanguages’
Authors: HUET GÉRARD
Published: March 2003

There is both a great unity and a great diversity in presentations of logic. The diversity is staggering indeed – propositional logic, first-order logic, higher-order logic
belong to one classification; linear logic, intuitionistic logic, classical logic, modal
and temporal logics belong to another one. Logical deduction may be presented as
a Hilbert style of combinators, as a natural deduction system, as sequent calculus, as
proof nets of one variety or other, etc. Logic, originally a field of philosophy, turned
into algebra with Boole, and more generally into meta-mathematics with Frege and
Heyting. Professional logicians such as Gödel and later Tarski studied mathematical models, consistency and completeness, computability and complexity issues, set
theory and foundations, etc. Logic became a very technical area of mathematical
research in the last half century, with fine-grained analysis of expressiveness of subtheories of arithmetic or set theory, detailed analysis of well-foundedness through
ordinal notations, logical complexity, etc. Meanwhile, computer modelling developed
a need for concrete uses of logic, first for the design of computer circuits, then more
widely for increasing the reliability of sofware through the use of formal specifications and proofs of correctness of computer programs. This gave rise to more
exotic logics, such as dynamic logic, Hoare-style logic of axiomatic semantics, logics
of partial values (such as Scott's denotational semantics and Plotkin's domain theory) or of partial terms (such as Feferman's free logic), etc. The first actual attempts
at mechanisation of logical reasoning through the resolution principle (automated
theorem proving) had been disappointing, but their shortcomings gave rise to a considerable body of research, developing detailed knowledge about equational reasoning through canonical simplification (rewriting theory) and proofs by induction
(following Boyer and Moore successful integration of primitive recursive arithmetic
within the LISP programming language). The special case of Horn clauses gave rise
to a new paradigm of non-deterministic programming, called Logic Programming,
developing later into Constraint Programming, blurring further the scope of logic.
In order to study knowledge acquisition, researchers in artificial intelligence and
computational linguistics studied exotic versions of modal logics such as Montague
intentional logic, epistemic logic, dynamic logic or hybrid logic. Some others tried
to capture common sense, and modeled the revision of beliefs with so-called non-monotonic logics. For the careful crafstmen of mathematical logic, this was the final
outrage, and Girard gave his anathema to such “montres à moutardes”.
TinkerType: a language for playing with formal systems
Authors: LEVIN MICHAEL Y. , PIERCE BENJAMIN C.
Published: March 2003

TinkerType is a pragmatic framework for compact and modular description of formal systems
(type systems, operational semantics, logics, etc.). A family of related systems is broken down
into a set of clauses – individual inference rules – and a set of features controlling the inclusion
of clauses in particular systems. Simple static checks are used to help maintain consistency
of the generated systems. We present TinkerType and its implementation and describe
its application to two substantial repositories of typed lambda-calculi. The first repository
covers a broad range of typing features, including subtyping, polymorphism, type operators
and kinding, computational effects, and dependent types. It describes both declarative and
algorithmic aspects of the systems, and can be used with our tool, the TinkerType Assembler, to
generate calculi either in the form of typeset collections of inference rules or as executable ML
typecheckers. The second repository addresses a smaller collection of systems, and provides
modularized proofs of basic safety properties.
Termination of rewriting in the Calculus of Constructions
Authors: WALUKIEWICZ-CHRZĄSZCZ DARIA
Published: March 2003

We show how to incorporate rewriting into the Calculus of Constructions and we prove that
the resulting system is strongly normalizing with respect to beta and rewrite reductions. An
important novelty of this paper is the possibility to define rewriting rules over dependently
typed function symbols. We prove strong normalization for any term rewriting system, such
that all function symbols satisfy the, so called, star dependency condition, and every rule is
accepted by the Higher Order Recursive Path Ordering (which is an extension of the method
created by Jouannaud and Rubio for the setting of the simply typed lambda calculus). The
proof of strong normalization is done by using a typed version of reducibility candidates due
to Coquand and Gallier. Our criterion is general enough to accept definitions by rewriting
of many well-known higher order functions, for example dependent recursors for inductive
types or proof carrying functions. This makes it a very good candidate for inclusion in a
proof assistant based on the Curry-Howard isomorphism.
A fully adequate shallow embedding of the
π-calculus in Isabelle/HOL with mechanized syntax analysis
Authors: RÖCKL CHRISTINE , HIRSCHKOFF DANIEL
Published: March 2003

This paper discusses an application of the higher-order abstract syntax technique to general-purpose theorem proving, yielding shallow embeddings of the binders of formalized languages.
Higher-order abstract syntax has been applied with success in specialized logical frameworks
which satisfy a closed-world assumption. As more general environments (like Isabelle/HOL
or Coq) do not support this closed-world assumption, higher-order abstract syntax may yield
exotic terms, that is, datatypes may produce more terms than there should actually be in the
language. The work at hand demonstrates how such exotic terms can be eliminated by means
of a two-level well-formedness predicate, further preparing the ground for an implementation
of structural induction in terms of rule induction, and hence providing fully-fledged syntax
analysis. In order to apply and justify well-formedness predicates, the paper develops a proof
technique based on a combination of instantiations and reabstractions of higher-order terms.
As an application, syntactic principles like the theory of contexts (as introduced by Honsell,
Miculan, and Scagnetto) are derived, and adequacy of the predicates is shown, both within a
formalization of the π-calculus in Isabelle/HOL.
The nosology of involuntary movements in older people
Authors: Meara Jolyon , Hobson Peter
Published: March 2003

Involuntary movements become increasingly common with age and often lead to considerable
disability, handicap and social embarrassment. Many causes of involuntary movements can be
readily treated once the correct diagnosis is established. Getting the diagnosis right in older
people is often challenging even for specialists. Even the identification of conditions thought
easy to classify in younger people, such as Parkinson's disease, can be very difficult in
older adults. This burden of movement disorder in older people reflects the increasing prevalence
of neurodegenerative and vascular disease with age as well as the growing exposure to medication and the natural history of conditions such as essential tremor, which tend to worsen with age and precipitate medical presentation later in life. A complex and poorly understood relationship exists between motor control, disorders of mood and cognitive function. In older subjects involuntary movements are often associated with gait abnormalities and poor mobility and falls may be the presenting feature.
Nurses' and elderly patients’ perceptions
regarding autonomy, privacy and informed
consent in nursing interventions in Greece
Authors: Lemonidou Chryssoula , Merkouris Anastasios , Leino-Kilpi Helena , Välimäki Maritta , Dassen Theo , Gasull Maria , Scott P Anne , Papathanassoglou Elizabeth , Arndt Marianne
Published: March 2003

Ethics increasingly becomes a forefront issue in health care decision-making, as health care becomes more technologically and organizationally complex. Hence, a great number of new laws on the status and rights of patients and professional codes have been adopted in Europe. However, research suggests that violation of patients’ rights of autonomy, informed consent and privacy may still be common, especially in elderly care.
The early environment, developmental plasticity and aging
Authors: Sayer Avan Aihie , Barker David
Published: March 2003

Darwin described how animal populations have two adaptation strategies: natural selection based on genetic variation acting over many generations, and developmental plasticity acting within the
lifetime of an individual. The contribution of these processes can be difficult to distinguish at the individual level, and the relevance of human
developmental plasticity to aging and health in later life is only now being recognized. The formal definition of developmental plasticity is ‘the ability of a single genotype to produce more than one alternative form of structure, physiological state or behaviour in response to environmental conditions’. As an alternative to adaptation to changing environments through genetic diversification, living things have evolved plastic responses. This enables the production of phenotypes that are better suited to their environment than would be possible if the same phenotype was produced regardless of environmental conditions
Appropriate prescribing in older people
Authors: Thomson S , Crome P
Published: March 2003

It is clearly established that older people suffer a high rate of disease related to medication. Probably the major reason for this is that older patients are prescribed more drugs than younger people and the rate of prescribing appears to be increasing all the time. In the UK, data are
currently collected on all prescriptions dispensed and this shows that older patients (aged over 65 years) receive 35-40% of all drugs prescribed. Between 1977 and 1988,
prescription items increased by 17% overall, but by 52% in people over 65 years. compared to only 1% in adults under 65. Prescription rates are rising for a number of reasons, including new advances in therapeutics, a rapidly enlarging older population,
moves to treat older patients more effectively (i.e. a less agist policy), rising patient expectations and defensive medical practice.
Falls
Authors: Colledge N
Published: March 2003

Falls have always been a major health issue for older people, but over the past few years
there has been an explosion of interest in their prevention. We are now at the challenging stage
of incorporating best evidence into routine clinical practice. This has been recognized by the
UK government in its National Service Framework for Older People in England, which has set
targets to reduce the number of falls that result in serious injury, and to ensure effective
treatment and rehabilitation for those who have fallen.
Cognitive changes in elderly people: the boundary between physiological aging and dementia
Authors: Derousené Christian
Published: March 2003

Cognitive impairment is one of the major health problems facing elderly people in the new
millennium. This does not only refer to dementia, but also to lesser degrees of cognitive deficit
that are associated with a decreased quality of life and, in many cases, progress to dementia.
Some studies suggest that delaying the emergence of dementia for a few years would result in a
considerable decrease in the human and economic burden related to the condition.
Dementia in the community: Challenges for primary care development
Authors: Iliffe Steve , Manthorpe Jill
Published: March 2003

The National Service Frameworks for Older People and for Mental Health are setting standards for services in areas where problems are complex and solutions limited. Primary Care Trusts seeking to raise the quality of primary care for older people and commission specialist services rationally face many challenges. Specialists in old age medicine and old age psychiatry will find themselves working closely with primary care practitioners to develop services and extend professional skills, for it is uncertain that specialist services will be able to deal with the scale of the clinical and social problems unaided.
Bladder and bowel problems after stroke
Authors: Barrett JA
Published: March 2003

The purpose of this review is to explore the evidence currently available and to identify the
framework within which to consider bladder and bowel emptying problems following a stroke.
The author was a member of the Intercollegiate Working Party for Stroke Continence Subgroup
that reviewed the evidence for the National Guidelines. The review is based on the author’s
personal knowledge of published and unpublished work. References in large textbooks and in the
landmark papers were checked and a Medline search was performed using the terms stroke,
cerebrovascular disease, incontinence and constipation.
Recent work in shape-based methods for diffusive inverse problems
Authors: Boverman Gregory , Khames ben Hadj Miled Mohamed , Miller Eric L.
Published: March 2003

We consider geometric inversion methods designed to directly determine information concerning the size, shape, location, and perhaps number of anomalies in a region of interest [E. L. Miller, M. E. Kilmer, and C. M. Rappaport, IEEE Trans. Geosci. Remote Sens. 38, 1682 (2000); O. Dorn, E. L. Miller, and C. Rappaport, Inverse Probl. 16, 1119 (2000)] for diffusive inverse problems arising in medical imaging and environmental remediation. First, a parametric approach to the problem is derived and validated using a diffuse optical tomography sensing example. A second technique to identify boundaries of an unknown number of objects is based on the idea of curve evolution. This approach mathematically “shrink wraps” a deformable surface in 3D or curve in 2D to the boundary of one or more objects. We demonstrate the utility of this method using an electrical resistance tomography sensing example in three dimensions.
Versatile high resolution crystal spectrometer with x-ray charge coupled device detector
Authors: Barnsley R. , Peacock N. J. , Dunn J. , Melnick I. M. , Coffey I. H. , Rainnie J. A. , Tarbutt M. R. , Nelms N.
Published: March 2003

A family of Johann configuration curved crystal spectrometers has been designed to share the basic engineering features of compactness, modularity, facility of alignment and focus, and incorporation of solid-state charge coupled device detector arrays. These detectors have intrinsically low noise, useful energy resolution, two-dimensional position sensitivity, and readout modes that are programmable. The spectrometers, although relatively compact, with a Rowland circle diameter in the range 0.5–2 m, can still have sufficient resolving power, dispersion, and throughput to be invaluable in high resolution studies of atomic and plasma sources. This article discusses the basic design features and performance of these doubly dispersive spectrometers and illustrates their versatility by applications to studies of a wide range of laboratory x-ray sources such as line emission from highly ionized atoms in the extended plasmas of Tokamaks and nearly point plasmas produced by focused laser irradiation of solids and in beam-foil experiments and electron beam ion traps.
Adaptive optics approach for prefiltering of geometrical fluctuations of the input laser beam of an interferometric gravitational waves detector
Authors: Calloni E. , Baker J. T. , Barone F. , DeRosa R. , Di Fiore L. , Milano L. , Restaino S. R.
Published: March 2003

In this article we present a preliminary study and experimental results on the use of an adaptive optics (AO) system for the reduction of geometrical fluctuations in a laser beam. The AO system is based on a Shack–Hartmann wave front sensor and a micromachined deformable mirror as a corrective element. The aim of this work is to investigate the applicability of such technologies to improving wave front clean-up conditions in long baseline interferometric gravitational wave detection.
Stray capacitance contribution to the electrical measurement of contact angles and areas
Authors: Quinn Anthony , Attard Phil
Published: March 2003

The capacitance of two parallel disks of finite unequal size is calculated by a variational procedure based on the electrostatic energy. It is found that effects due to the edges and the asymmetry can be substantial unless the radii of the disks are very much greater than the thickness of the dielectric interlayer. The trends predicted by the calculations are confirmed by measurements of the capacitance of electrodes deposited on polymer films and of water droplets. The implications for the electrical measurement of the contact angle or contact area of a droplet, and for the dependence of the contact angle on the applied potential in electrowetting, are discussed.
Ellipsometric study of silicon nanocrystal optical constants
Authors: Amans D. , Callard S. , Gagnaire A. , Joseph J. , Ledoux G. , Huisken F.
Published: March 2003

Samples of silicon nanocrystals on various substrates were prepared by cluster beam deposition of silicon nanoparticles, obtained by laser-induced pyrolysis of silane in a flow reactor. Using optical ellipsometry, the optical properties (refractive index and extinction coefficient) of the as-prepared silicon nanocrystal layers were determined in the wavelength range from 240 to 700 nm. Two dispersion models were used to describe the silicon nanocrystal optical properties: the Bruggeman effective medium approximation model and the Tauc–Lorentz model. The study showed that while a simple Bruggeman effective medium approximation model could not completely account for the silicon nanocrystal dispersion behavior, the optical response of the silicon nanocrystal layers could be satisfactorily described by a Tauc–Lorentz model. The present study also showed that, as for porous silicon, the silicon nanocrystal optical indexes significantly deviate from those of bulk crystalline and amorphous silicon. It confirms the special behavior of silicon under its nanoscale form.
Electronic and chemical properties of mixed-metal oxides: Adsorption and reaction of NO on SrTiO3(100)
Authors: Rodriguez J. A. , Azad S. , Wang L.-Q. , Garcı́a J. , Etxeberria A. , González L.
Published: March 2003

The interaction of NO with SrTiO3(100) surfaces was investigated using thermal desorption, photoemission, and first-principles density-functional calculations. The crystals used in the experiments exposed mainly (>80%) the TiO2-terminated face of SrTiO3(100). On the stoichiometric surfaces, the adsorption of NO was completely reversible at submonolayer coverages. Clear peaks for desorption of NO were found at 125 (multilayer state), 160, and 260 K, plus a long tail between 300 and 450 K. Desorption of N2O was detected only near 125 K with the multilayer of NO. DF calculations give adsorption energies of 14 and 6 kcal/mol for NO on the TiO2- and SrO-terminated faces of SrTiO3(100), which are consistent with the peaks at 260 and 160 K seen in thermal desorption. On the TiO2-terminated face of SrTiO3(100), there is substantial hybridization between the orbitals of NO and the oxide bands. This is not seen on the SrO-terminated face, where the large positive charge on the Sr sites leads to weak adsorption bonds. A reaction channel for the production of N2O and N2 is opened by partially reducing the SrTiO3(100) surface. The cleavage of N–O bonds produces adatoms that quench vacancy states in the valence region and reduce the signals for Ti3+ and Ti2+ cations in core-level photoemission. DF calculations indicate that the adsorption of a NO single molecule over a vacancy site is a highly exothermic process (⩾70 kcal/mol) that leads to a large elongation (∼0.20 Å) but not a complete rupture of the N–O bond. The dissociation of this bond is facilitated by the addition of a second NO molecule and formation of an ON–NO dimer. The behavior of SrTiO3 illustrates the important effects that metal↔oxygen↔metal interactions can have on the electronic and chemical properties of a mixed-metal oxide. When dealing with the design or performance of ABO3 perovskite catalysts, a simple extrapolation of the catalytic properties of the individual AO and BO2 oxides may not be a reliable approach.
The rotational spectrum of iodine dioxide, OIO
Authors: Miller Charles E. , Cohen Edward A.
Published: March 2003

The rotational spectrum of the OIO radical has been observed for the first time. Spectra of both the ground and first two excited bending vibrational states have been analyzed. Rotational, centrifugal distortion, fine, and hyperfine constants have been derived. These constants have been used to determine the molecular structure, harmonic force field, and electron distribution. The OIO molecular parameters are compared with those of OClO and OBrO.
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-type interface defects in (100)Si/SiO2 structures grown in ozonated water solution
Authors: Pierreux D. , Stesmans A.
Published: March 2003

Si dangling bond interface defects (Pb0,Pb1) were probed by electron spin resonance in entities of (100)Si with ultrathin SiO2 grown in ozonated de-ionized water solution at room temperature. After photodesorption of passivating hydrogen, Pb0 appears with densities up to ∼5×1012 cm−2, a value five times larger than the one standardly attained with high temperature thermal growth. Thus standard quality thermal Si/SiO2 interface properties, as exposed by the Pb0-type defects criterion (interface traps), are not obtained by oxidation in ozonated water solutions at room temperature. The interface quality may be upgraded by providing additional thermal budget. Yet standard qualitity is still not attained after vacuum annealing at 600 °C.
Particle transport phenomena in low-temperature solids (Review)
Authors: Bargheer M. , Schwentner N.
Published: March 2003

We review different approaches to measure the transport of F atoms and ions in rare-gas matrices and compare the experimental results to simulations. Static measurements on sandwich structures and co-doped matrices yield rather long travel ranges beyond 2 nm, in accord with early classical simulations which predict a channeling of the F atoms in rare gas matrices. Nonadiabatic simulations show a rapid energy loss, fast nonadiabatic dynamics, and only short travel ranges of typically 1 unit cell. The rapid energy loss, fast nonadiabatic transitions and the time scale for direct dissociation (∼250 fs) are verified by femtosecond pump–probe experiments. It remains a challenge to account for the long-range migration when nonadiabatic processes are allowed in simulations, and to measure the long-distance flights directly by ultrafast spectroscopy.
Coherent motion and anomalous transport properties of exciton and hole polarons with intrinsic vibrational structure
Authors: Ratner A. M.
Published: March 2003

It is shown that intrinsic vibrational degrees of freedom, inherent in two-atom exciton and hole polarons, drastically affect their transport properties in wide-band dielectrics (rare-gas solids and alkali halides). A fast excitonic energy transport and a comparatively high hole mobility, experimentally observed and attributed to two-site polarons tightly bound with the lattice, cannot be explained by the conventional theory of small-radius polarons that predicts their negligibly weak diffusion, exponentially small in the ratio of the binding energy to temperature. The theory developed below with allowance for the intrinsic vibrational structure of two-site polarons describes qualitatively a large relevant set of experimental data which seem anomalous from the viewpoint of the conventional theory.
Excess electron transport in cryoobjects
Authors: Eshchenko D. G. , Storchak V. G. , Brewer J. H. , Cottrell S. P. , Cox S. F. J.
Published: March 2003

Experimental results on excess electron transport in solid and liquid phases of Ne, Ar, and solid N2–Ar mixture are presented and compared with those for He. The muon spin relaxation technique in frequently switching electric fields was used to study the phenomenon of delayed muonium formation: excess electrons liberated in the μ+ ionization track converge upon the positive muons and form Mu (μ+e−) atoms. This process is shown to be crucially dependent upon the electron’s interaction with its environment (i.e., whether it occupies the conduction band or becomes localized in a bubble of tens of angstroms in radius) and upon its mobility in these states. The characteristic lengths involved are 10−6–10−4 cm, and the characteristic times range from nanoseconds to tens of microseconds. Such a microscopic length scale sometimes enables the electron to spend its entire free lifetime in a state which may not be detected by conventional macroscopic techniques. The electron transport processes are compared in: liquid and solid helium (where the electron is localized in a bubble); liquid and solid neon (where electrons are delocalized in the solid, and the coexistence of localized and delocalized electron states in the liquid was recently found); liquid and solid argon (where electrons are delocalized in both phases); orientational glass systems (solid N2–Ar mixtures), where our results suggest that electrons are localized in an orientational glass. This scaling from light to heavy rare gases enables us to reveal new features of excess-electron localization on a microscopic scale. Analysis of the experimental data makes it possible to formulate the following tendency of the muon end-of-track structure in condensed rare gases. The muon–self-track interaction changes from isolated-pair (muon plus the nearest track electron) in helium to multipair (muon in the vicinity of tens of track electrons and positive ions) in argon.
Low-temperature electron transport on semiconductor surfaces
Authors: Lastapis M. , Riedel D. , Mayne A. , Bobrov K. , Dujardin G.
Published: March 2003

The low-temperature electron transport on semiconductor surfaces has been studied using an ultrahigh-vacuum, variable temperature scanning tunneling microscope (STM). The STM I(V) spectroscopy performed at various temperatures has made it possible to investigate the temperature dependence (300 K to 35 K) of the surface conductivity of three different semiconductor surfaces: highly doped n-type Si(100), p-type Si(100), and hydrogenated C(100). Low temperature freezing of specific surface electronic channels on the highly doped n-type Si(100) and moderately doped p-type Si(100) surfaces could be achieved, whereas the total surface conductivity on the hydrogenated C(100) surface can be frozen below only 180 K.
Reactions induced by low energy electrons in cryogenic films (Review)
Authors: Bass A. D. , Sanche L.
Published: March 2003

We review recent research on reactions (including dissociation) initiated by low-energy electron bombardment of monolayer and multilayer molecular solids at cryogenic temperatures. With incident electrons of energies below 20 eV, dissociation is observed by the electron stimulated desorption (ESD) of anions from target films and is attributed to the processes of dissociative electron attachment (DEA) and to dipolar dissociation. It is shown that DEA to condensed molecules is sensitive to environmental factors such as the identity of co-adsorbed species and film morphology. The effects of image-charge induced polarization on cross sections for DEA to CH3Cl are also discussed. Taking as example, the electron-induced production of CO within multilayer films of methanol and acetone, it is shown that the detection of electronic excited states by high-resolution electron energy loss spectroscopy can be used to monitor electron beam damage. In particular, the incident energy dependence of the CO indicates that below 19 eV, dissociation proceeds via the decay of transient negative ions (TNI) into electronically excited dissociative states. The electron-induced dissociation of biomolecular targets is also considered, taking as examples the ribose analog tetrahydrofuran and DNA bases adenine and thymine, cytosine and guanine. The ESD of anions from such films also show dissociation via the formation of TNI. In multilayer molecular solids, fragment species resulting from dissociation, may react with neighboring molecules, as is demonstrated in anion ESD measurements from films containing O2 and various hydrocarbon molecules. X-ray photoelectron spectroscopy measurements reported for electron-irradiated monolayers of H2O and CF4 on a Si–H passivated surface further show that DEA is an important initial step in the electron-induced chemisorption of fragment species.
Effects of electron irradiation on structure and bonding of SF6 on Ru(0001)
Authors: Faradzhev N. S. , Kusmierek D. O. , Yakshinskiy B. V. , Madey T. E.
Published: March 2003

Electron-stimulated desorption ion angular distribution (ESDIAD) and temperature-programmed desorption (TPD) techniques have been employed to study radiation-induced decomposition of fractional monolayer SF6 films physisorbed on Ru(0001) at 25 K. Our focus is on the origin of F+ and F− ions, which dominate ESD from fractional monolayers. F− ions escape only in off-normal directions and originate from undissociated molecules. The origins of F+ ions are more complicated. The F+ ions from electron-stimulated desorption of molecularly adsorbed SF6 desorb in off-normal directions, in symmetric ESDIAD patterns. Electron beam exposure leads to formation of SFx (x=0–5) fragments, which become the source of positive ions in normal and off-normal directions. Electron exposure >1016 cm−2 results in decomposition of the entire adsorbed SF6 layer.
Soft landing of size-selected clusters in rare gas matrices
Authors: Lau J. T. , Wurth W. , Ehrke H.-U. , Achleitner A.
Published: March 2003

Soft landing of mass-selected clusters in rare gas matrices is a technique used to preserve mass selection in cluster deposition. To prevent fragmentation upon deposition, the substrate is covered with rare gas matrices to dissipate the cluster kinetic energy upon impact. Theoretical and experimental studies demonstrate the power of this technique. Besides STM, optical absorption, excitation, and fluorescence experiments, x-ray absorption at core levels can be used as a tool to study soft landing conditions, as will be shown here. X-ray absorption spectroscopy is also well suited to follow diffusion and agglomeration of clusters on surfaces via energy shifts in core level absorption.
Element-specific and site-specific ion desorption from adsorbed molecules by deep core-level photoexcitation at theK-edges
Authors: Baba Y.
Published: March 2003

This article reviews our recent work on the ion desorption from adsorbed and condensed molecules at low temperature following the core-level photoexcitations using synchrotron soft x-rays. The systems investigated here are adsorbed molecules with relatively heavy molecular weight, containing third-row elements such as Si, P, S, and Cl. Compared with molecules composed of second-row elements, the highly element-specific and site-specific fragment-ion desorptions are observed when we tune the photon energy at the dipole-allowed 1s→σ*(3p*) resonance. On the basis of the resonance Auger decay spectra around the 1s ionization thresholds, the observed highly specific ion desorption is interpreted in terms of the localization of the excited electrons (here called “spectator electrons”) in the antibonding σ* orbital. In order to separate the direct photo-induced process from the indirect processes triggered by the secondary electrons, the photon-stimulated ion desorption was also investigated in well-controlled mono- and multilayer molecules. The results confirmed that the resonant photoexcitation not in the substrate but in the thin films of adsorbates plays a significant role in the realization of the highly specific ion desorption.
Ion desorption from molecules condensed at low temperature: A study with electron-ion coincidence spectroscopy combined with synchrotron radiation (Review)
Authors: Mase Kazuhiko , Nagasono Mitsuru , Tanaka Shin-ichiro , Sekitani Tetsuji , Nagaoka Shin-ichi
Published: March 2003

This article reviews our recent work on photostimulated ion desorption (PSID) from molecules condensed at low temperature. We have used electron–ion coincidence (EICO) spectroscopy combined with synchrotron radiation. The history and present status of the EICO apparatus is described, as well as our recent investigations of condensed H2O, NH3, CH3CN, and CF3CH3. Auger electron photon coincidence (AEPICO) spectra of condensed H2O at the O:1s ionization showed that H+ desorption was stimulated by O:KVV Auger processes leading to two-hole states (normal-Auger stimulated ion desorption (ASID) mechanism). The driving forces for H+ desorption were attributed to the electron missing in the O–H bonding orbitals and the effective hole–hole Coulomb repulsion. The normal ASID mechanism was also demonstrated for condensed NH3. The H+ desorption at the 4a1←O(N):1s resonance of both condensed H2O and condensed NH3 was found to be greatly enhanced. Based on the AEPICO spectra the following four-step mechanism was proposed: (1) the 4a1←1s transition, (2) extension of the HO–H (H2N–H) distance within the lifetime of the (1s)−1(4a1)1 state, (3) spectator Auger transitions leading to (valence)−2(4a1)1 states, and (4) H+ desorption. The enhancement of the H+ desorption yield was attributed to the repulsive potential surface of the (1s)−1(4a1)1 state. At the 3p←O:1s resonance of condensed H2O, on the other hand, the H+ yield was found to be decreased. The AEPICO spectra showed that the H+ desorption was stimulated by spectator Auger transitions leading to (valence)−2(3p)1 states. The decrease in the H+ yield was attributed to a reduction in the effective hole–hole Coulomb repulsion due to shielding by the 3p electron. Photoelectron photon coincidence (PEPICO) spectra of condensed H2O showed that the core level of the surface H2O responsible for the H+ desorption was shifted by 0.7 eV from that of the bulk H2O. The H+ desorption from condensed CH3CN was also investigated. In a study of condensed CF3CH3 using PEPICO spectroscopy, site-specific ion desorption was directly verified; that is, H+ and CH3+ desorption was predominant for the C:1s photoionization at the -CH3 site, while C2Hn+, CFCHm+, and CF3+ desorption was predominantly induced by the C:1s photoionization at the -CF3 site. These investigations demonstrate that EICO spectroscopy combined with synchrotron radiation is a powerful tool for studying PSID of molecules condensed at low temperature.
Absolute yields of the exciton-induced desorption at the surface of solid rare gases
Authors: Arakawa I. , Adachi T. , Hirayama T. , Sakurai M.
Published: March 2003

Absolute yields of the photo-induced desorption at the surface of solid rare gases are studied in the excitonic excitation region. Both metastable and total desorption yields depend strongly on excitation energy and film thickness of rare gas solids. The absolute desorption yields and their dependence on film thickness are quantitatively reproduced by a simulation based on the diffusion of excitons in the bulk and the kinetic energy release by a cavity ejection mechanism and an excimer dissociation mechanism followed by internal sputtering.
Biexcitons in solid neon
Authors: Wiethoff P. , Kassühlke B. , Menzel D. , Feulner P.
Published: March 2003

We study the creation of biexcitons in neon films on a metal substrate by one-photon processes. We demonstrate that photon-stimulated desorption of ions is a perfect tool for the investigation of these excitation processes, which possess very low cross sections. We show that the principle of the equivalent-core approximation which is well known from inner shell experiments can also be applied to the neon biexciton case. Comparing the equivalent-core molecules Ne2** and Na2, we find that neon biexcitons can be described well in a Frenkel picture.
Exciton-induced lattice defect formation
Authors: Savchenko E. V. , Ogurtsov A. N. , Zimmerer G.
Published: March 2003

The lattice defect formation induced by electronic excitation in solid Ne is studied using the selective vacuum ultraviolet spectroscopy method. The samples are excited with synchrotron radiation in the range of excitonic absorption n=2Γ(3/2). The dose dependence of the intensity distribution in the band of atomic-type self-trapped exciton luminescence is analyzed. Direct evidence of the formation and accumulation of point lattice defects in solid Ne via the excitonic mechanism is obtained for the first time. A model of permanent lattice defect formation is discussed.
Neutral particle analyzer/isotope separator for measurement of hydrogen isotope composition of JET plasmas
Authors: Afanasyev V. I. , Gondhalekar A. , Babenko P. Yu. , Beaumont P. , De Antonis P. , Detch A. V. , Kislyakov A. I. , Kozlovskij S. S. , Mironov M. I. , Petrov M. P. , Petrov S. Ya. , Tschernyshev F. V. , Wilson C. H. ,   Contributors to the EFDA-JET Workprogramme
Published: March 2003

This article describes a neutral particle analyzer/isotope separator (ISEP) developed for measurement of the relative hydrogen isotope composition of Joint European Torus (JET) plasmas. The ISEP deployed on the JET can be regarded as a prototype of an instrument proposed for measurement of the spatial profile of the ratio of the density of deuterium and tritium ions in the plasma, nD(r)/nT(r), in the International Thermonuclear Experimental Reactor (ITER). The ISEP makes simultaneous measurements of the energy distribution of efflux of hydrogen isotope atoms (H, D, and T) from the plasma. From such measurements it is possible to deduce the radial profile of the relative hydrogen isotope ion composition of the plasma and radial transport of ions of one isotope across the plasma of another isotope species. The main elements of the ISEP are (a) use of a thin carbon foil for reionization of the incident atoms, thereby eliminating gas stripping cells and gas sources of conventional neutral particle analyzers (NPAs), (b) acceleration of secondary ions in order to access the regime of higher detection efficiency of the NPA and to better separate ion pulses from neutron/γ-ray induced pulses in scintillator detectors, (c) E‖B dispersion of the secondary ions in specially designed nonuniform magnetic and electric fields to provide focusing in the detector plane, increased throughput and greater contrast between neighboring isotopes, and (d) counting of energy and mass analyzed secondary ions using detectors consisting of thin [1⩽t (μm)⩽7] CsI(Tl) scintillators deposited directly on miniature thin window photomultiplier tubes mounted in vacuum. The ISEP has high contrast between atoms of neighboring masses (⩾103 for E≈5 keV and much greater at higher energies), and high detection efficiency (0.06⩽ε⩽0.83 for atoms of 5⩽ (keV)⩽150. ISEP detectors have very low sensitivity to neutrons and γ rays (⩽10−7 of ion sensitivity), making it feasible to use the ISEP in JET DT experiments without any shielding. Only a modest amount of neutron/γ-ray shielding would be required in the ITER for similar applications of the ISEP. The initial experiments on JET plasmas using the ISEP demonstrate well the capabilities of the instrument for measurement of the hydrogen isotope composition of the plasma and the energy distribution function of isotope ions.
Optimization of the number of soft x-ray arrays and detectors for the SST-1 tokamak by the tomographic method
Authors: Chattopadhyay A. K. , Rao C. V. S. , Srivatsan R.
Published: March 2003

An x-ray imaging system for tomographic reconstruction of two-dimensional emissivity is being developed for the SST-1 tokamak. In this article it is shown that for circular plasma, which will be generated in the first phase of operation of the machine, 7 arrays and 115 detectors are adequate to reconstruct the simulated data. Sawtooth phenomena depicted by both the Wesson model and the Kadomtsev model and the disruption phenomenon associated with m=2 mode are reconstructed well with the help of this imaging system.
Direct current slice imaging
Authors: Townsend Dave , Minitti Michael P. , Suits Arthur G.
Published: March 2003

We report a new variation of the velocity map ion imaging method that allows the central section of the photofragment ion cloud to be recorded exclusively. The relevant speed and angular distributions for a molecular photodissociation or scattering event may therefore be obtained without need to utilize inversion methods such as the inverse Abel transform. In contrast to the recently reported “slicing” technique of Kitsopoulos and co-workers [C. R. Gebhardt et al., Rev. Sci. Instrum. 72, 3848 (2001)], our method makes no use of grids or pulsed electric fields which can distort the photofragment cloud and therefore compromise the resolution of velocity mapping. We find that by operating a multilens velocity mapping assembly at low voltages, the ion cloud stretches in the acceleration region owing to the kinetic energy release in the fragments. Furthermore, this inherent stretching is sufficient to allow the central section of the distribution to be recorded exclusively by application of a narrow time gate (∼40 ns) to a position sensitive detector. We have performed extensive ion trajectory simulations to understand this “direct current (dc) slice imaging” technique, and experimentally we have applied it to the 355 nm dissociation of Cl2 and NO2 as well-understood test cases. In the Cl2 studies the velocity resolution obtained for the Cl35 fragments is on the order of Δν/ν=2.8% and for the first time we are able to directly observe dissociation via the weak B 3Π0u+ state channel whilst imaging the ground state Cl(2P3/2)-atom distribution. For the case of NO2 dissociation the internal state distributions of the NO fragment are extracted more cleanly using slicing than is possible with the Abel inversion and our resolution is sufficient to resolve some of the NO rotational structure in the kinetic energy release for the first time. Overall, we find our data to compare very favorably with previously reported results and conclude that dc slice imaging offers an important, easily implemented refinement to the velocity mapping approach. We also demonstrate a second dc slice imaging method that records only the central section of an expanded photofragment distribution by using a probe laser displaced off-axis from the molecular beam. This approach, which we term “raster imaging,” may be particularly advantageous in two-color experiments where the probe laser also makes a significant contribution to the initial photolysis of the molecular species under investigation.
Indium content measurements in metamorphic high electron mobility transistor structures by combination of x-ray reciprocal space mapping and transmission electron microscopy
Authors: Chauveau J.-M. , Androussi Y. , Lefebvre A. , Di Persio J. , Cordier Y.
Published: March 2003

We propose a method to determine the indium concentrations x and y in the InyAl1−yAs/InxGa1−xAs metamorphic structures. This approach is based on the combination of two experimental techniques: (i) reciprocal space mapping (RSM) to determine the average In composition in the InAlAs layers and (ii) transmission electron microscopy (TEM) using the intensity measurements of the chemically sensitive (002) reflection from dark-field images to determine the composition in the InGaAs quantum well. We apply this method to a InyAl1−yAs/InxGa1−xAs metamorphic high electron mobility transistor, with x and y approximately equal to 0.35. Furthermore, we present an original and straightforward way to evaluate experimental errors in the determination of composition and strain with the RSM procedure. The influence of these errors on the TEM results is discussed. For In concentrations in the 30%–40% range, the accuracy of this simple method is about 0.5% on the In composition in the InGaAs quantum well.
Thermal conductivity calibration for hot wire based dc scanning thermal microscopy
Authors: Lefèvre Stéphane , Volz Sebastian , Saulnier Jean-Bernard , Fuentes Catherine , Trannoy Nathalie
Published: March 2003

Thermal conductivity characterization with nanoscale spatial resolution can be performed by contact probe techniques only. The technique based on a hot anemometer wire probe mounted in an atomic force microscope is now a standard setup. However, no rigorous calibration procedure is provided so far in basic dc mode. While in contact with the sample surface, the electrical current I injected into the probe is controlled so that electrical resistance or the wire temperature is maintained by the Joule effect. The variation in current is assumed to be linearly related to the heat flux lost towards the sample and traditional calibration is carried out by relating the thermal conductivity of a set of samples to the measured current I. We provide analytical and numerical thermal modeling of the tip and sample to estimate the key heat transfer in a conductivity calibration procedure. A simple calibration expression is established that provides thermal conductivity as a function of the probe current or voltage measured. Finally, experimental data allow us to determine the unknown quantities of the parametric form obtained, i.e., the mean tip–sample contact radius and conductance.
Laser transfer of biomaterials: Matrix-assisted pulsed laser evaporation (MAPLE) and MAPLE Direct Write
Authors: Wu P. K. , Ringeisen B. R. , Krizman D. B. , Frondoza C. G. , Brooks M. , Bubb D. M. , Auyeung R. C. Y. , Piqué A. , Spargo B. , McGill R. A. , Chrisey D. B.
Published: March 2003

Two techniques for transferring biomaterial using a pulsed laser beam were developed: matrix-assisted pulsed laser evaporation (MAPLE) and MAPLE direct write (MDW). MAPLE is a large-area vacuum based technique suitable for coatings, i.e., antibiofouling, and MDW is a localized deposition technique capable of fast prototyping of devices, i.e., protein or tissue arrays. Both techniques have demonstrated the capability of transferring large (mol wt>100 kDa) molecules in different forms, e.g., liquid and gel, and preserving their functions. They can deposit patterned films with spatial accuracy and resolution of tens of μm and layering on a variety of substrate materials and geometries. MDW can dispense volumes less than 100 pl, transfer solid tissues, fabricate a complete device, and is computed aided design/computer aided manufacturing compatible. They are noncontact techniques and can be integrated with other sterile processes. These attributes are substantiated by films and arrays of biomaterials, e.g., polymers, enzymes, proteins, eucaryotic cells, and tissue, and a dopamine sensor. These examples, the instrumentation, basic mechanisms, a comparison with other techniques, and future developments are discussed.
Magnetic and microwave magnetic properties of barium hexaferrite permanent magnet films having the c-axis in the film plane
Authors: Yoon S. D. , Vittoria C. , Oliver S. A.
Published: March 2003

Thick (1–14 μm) films of ferrimagnetic barium hexaferrite (BaFe12O19 or BaM) having the c-axis ([0001]) in the film plane were deposited by pulsed laser deposition onto a-plane (112¯0) sapphire (Al2O3) substrates, and were found to have a (101¯0) orientation. Torque and magnetization measurements show these films are permanent magnets with easy magnetization direction in the plane of the film. Ferrimagnetic resonance (FMR) spectra exhibited linewidths of 1.00–1.40 kOe, where low-field FMR measurements do not show uniform mode broadening due to the formation of multiple domains. All film parameters were affected by the large stress present in these films due to crystallographic and thermal mismatches. These films have dual functionality as gyrotropic media and permanent magnets, and are usable as either nonreciprocal microwave devices or biasing magnets.