496 research outputs found
Two-Sided Derivatives for Regular Expressions and for Hairpin Expressions
The aim of this paper is to design the polynomial construction of a finite
recognizer for hairpin completions of regular languages. This is achieved by
considering completions as new expression operators and by applying derivation
techniques to the associated extended expressions called hairpin expressions.
More precisely, we extend partial derivation of regular expressions to
two-sided partial derivation of hairpin expressions and we show how to deduce a
recognizer for a hairpin expression from its two-sided derived term automaton,
providing an alternative proof of the fact that hairpin completions of regular
languages are linear context-free.Comment: 28 page
Invariance: a Theoretical Approach for Coding Sets of Words Modulo Literal (Anti)Morphisms
Let be a finite or countable alphabet and let be literal
(anti)morphism onto (by definition, such a correspondence is determinated
by a permutation of the alphabet). This paper deals with sets which are
invariant under (-invariant for short).We establish an
extension of the famous defect theorem. Moreover, we prove that for the
so-called thin -invariant codes, maximality and completeness are two
equivalent notions. We prove that a similar property holds in the framework of
some special families of -invariant codes such as prefix (bifix) codes,
codes with a finite deciphering delay, uniformly synchronized codes and
circular codes. For a special class of involutive antimorphisms, we prove that
any regular -invariant code may be embedded into a complete one.Comment: To appear in Acts of WORDS 201
Electronic Spectroscopy of Jet-Cooled Benzylidenecyclobutane, a Sterically Hindered Styrene
The electronic spectrum of the styrene derivative, benzylidenecyclobutane, seeded in a supersonic jet expansion has been recorded using resonantly enhanced two-photon ionization spectroscopy. The main vibronic features in the spectrum are associated with a low frequency progression assigned to the torsional motion of the phenyl ring. Analysis of the observed torsional levels reveals an excited state potential energy surface characteristic of a planar equilibrium geometry which undergoes large amplitude motion and a ground state surface having a minimum at a torsional angle of 25° between the phenyl and vinyl groups. Ab initio calculations of the ground state torsional potential surface predict a minimum in the range of 28°-26°, depending on the size of the basis set. In these structures the cyclobutane ring adopts a puckering angle between 17° and 19°. Deuterated isotopomers have also been synthesized and their corresponding photoionization spectra analyzed to reveal the mixing between the torsion and other low frequency modes such as cyclobutane ring puckering. The extent of this mixing is found to be sensitive to the sites of deuteration on the molecule. © 1996 American Institute of Physics
Electronic Spectroscopy of Jet-Cooled Benzylidenecyclobutane, a Sterically Hindered Styrene
The electronic spectrum of the styrene derivative, benzylidenecyclobutane, seeded in a supersonic jet expansion has been recorded using resonantly enhanced two-photon ionization spectroscopy. The main vibronic features in the spectrum are associated with a low frequency progression assigned to the torsional motion of the phenyl ring. Analysis of the observed torsional levels reveals an excited state potential energy surface characteristic of a planar equilibrium geometry which undergoes large amplitude motion and a ground state surface having a minimum at a torsional angle of 25° between the phenyl and vinyl groups. Ab initio calculations of the ground state torsional potential surface predict a minimum in the range of 28°-26°, depending on the size of the basis set. In these structures the cyclobutane ring adopts a puckering angle between 17° and 19°. Deuterated isotopomers have also been synthesized and their corresponding photoionization spectra analyzed to reveal the mixing between the torsion and other low frequency modes such as cyclobutane ring puckering. The extent of this mixing is found to be sensitive to the sites of deuteration on the molecule. © 1996 American Institute of Physics
Altercentric bias in preverbal infants memory
Human infants would seem to face a daunting challenge in selecting what they should attend, encode and remember. We investigated whether early in life, infants might use othersâ attention as an exploitable source of information filtering, by prioritizing the encoding of events that are co-witnessed with someone else over events witnessed alone. In a series of studies (n=255), we show that infants who can otherwise remember an objectâs location, misremembered the object where another agent had seen it, even if infants themselves had subsequently seen the object move somewhere else. With further exploratory analyses, we also found that infantsâ attention to the agent rather than the object seems to drive their memory for the objectâs location. This series points to an initial encoding bias that likely facilitates information selection but which can, under some circumstances, lead to predictable memory errors
Conformations And Relative Stabilities Of The Cis And Trans Isomers In A Series Of Isolated N-phenylamides
The gas-phase conformations of a series of isolated N-phenylamides have been determined from vibrationally resolved electronic spectra obtained by resonant two-photon ionization in a supersonic jet expansion. Both the cis and trans isomers of formanilide were identified, with the cis isomer in 6.5% abundance. The spectral features displayed by this isomer are consistent with a nonplanar geometry which undergoes a large change in the phenyl torsional angle following electronic excitation. The more abundant trans isomer of formanilide adopts a planar structure and is stabilized by 2.5 kcal/mol with respect to the cis isomer. In the excited electronic state the relative stabilities of the two isomers are reversed. Acetanilide, in contrast, is found exclusively as the trans isomer, also having a planar structure. N-Methyl substitution causes a reversal of the relative isomer stabilities found in formanilide and leads to an isomer distribution consisting of approximately 90% E and 10% Z in N-methylformanilide. These experimental observations are compared to previous condensed phase structural determinations as well as to the relative energies and structures predicted from ab initio Hartree-Fock geometry optimizations
The Principle of Critical Energy as a Transdisciplinary Principle with Interdisciplinary Applications
The principle of critical energy (PCE) is a transdisciplinary principle that may be used in all chapters of sciences for superposition and/or cumulation of different external actions (mechanical, thermal, magnetic, electrical, chemical, etc.) It may be used for lifetime evaluation of engineering structures, as well as for living organisms, by taking into account the influences due to pollution, due to internal deterioration, due to preloading or residual stresses, etc. In this paper, we explain what PCE is, how it may be practically used and the interdependences between the terms comprised in its general relation. PCE was applied for solving problems of superposition of external actions and internal deteriorations in the following chapters of sciences: mechanical engineering, thermomechanical-chemical loadings, multiple pollution, medical field and viscoelasticity. It was compared with synergy theory and with catastrophe theory
Probing the N = 32 shell closure below the magic proton number Z = 20: Mass measurements of the exotic isotopes 52,53K
The recently confirmed neutron-shell closure at N = 32 has been investigated
for the first time below the magic proton number Z = 20 with mass measurements
of the exotic isotopes 52,53K, the latter being the shortest-lived nuclide
investigated at the online mass spectrometer ISOLTRAP. The resulting
two-neutron separation energies reveal a 3 MeV shell gap at N = 32, slightly
lower than for 52Ca, highlighting the doubly-magic nature of this nuclide.
Skyrme-Hartree-Fock-Boguliubov and ab initio Gorkov-Green function calculations
are challenged by the new measurements but reproduce qualitatively the observed
shell effect.Comment: 5 pages, 5 figure
Fault kinematics in northern Central America and coupling along the subduction interface of the Cocos Plate, from GPS data in Chiapas (Mexico), Guatemala and El Salvador
International audienceNew GPS measurements in Chiapas (Mexico), Guatemala and El Salvador are used to constrain the fault kinematics in the North America (NA), Caribbean (CA) and Cocos (CO) plates triple junction area. The regional GPS velocity field is first analysed in terms of strain partitioning across the major volcano-tectonic structures, using elastic half-space modelling, then inverted through a block model. We show the dominant role of the Motagua Fault with respect to the Polochic Fault in the accommodation of the present-day deformation associated with the NA and CA relative motion. The NA/CA motion decreases from 18-22 mm yrâ1 in eastern Guatemala to 14-20 mm yrâ1 in central Guatemala (assuming a uniform locking depth of 14-28 km), down to a few millimetres per year in western Guatemala. As a consequence, the western tip of the CA Plate deforms internally, with â9 mm yrâ1 of east-west extension (â5 mm yrâ1 across the Guatemala city graben alone). Up to 15 mm yrâ1 of dextral motion can be accommodated across the volcanic arc in El Salvador and southeastern Guatemala. The arc seems to mark the northern boundary of an independent forearc sliver (AR), pinned to the NA plate. The inversion of the velocity field shows that a four-block (NA, CA, CO and AR) model, that combines relative block rotations with elastic deformation at the block boundaries, can account for most of the GPS observations and constrain the overall kinematics of the active structures. This regional modelling also evidences lateral variations of coupling at the CO subduction interface, with a fairly high-coupling (â0.6) offshore Chiapas and low-coupling (â0.25) offshore Guatemala and El Salvador
- âŠ