A non-commutative version of the first alexandroff decomposition theorem in ordered topological groups

In this paper we establish a decomposition theorem for a positive regular measure on an orthoalgebra with values in an ordered topological group not necessarily commutative. We deduce from it the A. D. Alexandroff’s classical first decomposition theorem and we discuss its uniqueness in the setting of metric spaces.     

Acid extraction treatment of sediment samples for organotin speciation; occurrence of butyltin and phenyltin compounds on the cadiz coast,south-west spain

A method is described for leaching of nanogram amounts of mono-, di and tri-butyltin compounds and mono-, di- and tri-phenyltin compounds from sediments. The procedure is based on soaking the sediments in a water–hydrogen bromide mixture (2:3) with magnetic stirring for 1 h followed by extraction with 0.02% (w/v) tropolone solution in pentane for 2 h. Organotins are determined by GF FPD after clean-up through a Florisil column and derivatization by Grignard pentylation. The method has been applied to the study of water and sediments in different areas of south-west Spain. Predominant species are butyltins, especially tributyltin (TBT), which has high values in waters and sediments of Puerto de Santa Maria and Cadiz Bay, as well as in sediments of the Sancti Petri Channel, which suggests a harmful action on biota. A direct relation has been found beween organotin levels and distance of potential focus determined by boating activities. In addition, the relative occurrence of dibutyltin (DBT) and monobutyltin (MBT) together with TBT has been noted, possibly as a result of a degractation process, and the influence of grain size of sediment and presence of organic matter on organotin accumulation has been studied.     

Eigentensors of the Lichnerowicz operator in Euclidean Schwarzschild metrics

Properties of the eigentensors of the Lichnerowicz Laplacian for the Euclidean Schwarzschild metric are discussed together with possible applications to the linear stability of higher‐dimensional instantons. The main statement of the article is that any eigentensor of the Lichnerowicz operator in a Euclidean (possibly higher‐dimensional) Schwarzschild metric is essentially singular at infinity.     

Existence theorems for m-accretive operators in Banach spaces

In 1985, the second author proved a surjective result for m-accretive and ?-expansive mappings for uniformly smooth Banach spaces. However, in this case, we have been able to remove the uniform smoothness of the Banach space, without any additional assumption.     

Ultrafine layered LiCoO2 obtained from citrate precursors

A new method for the preparation of ultrafine LiCoO₂ with a layered crystal structure was developed, which consists in thermal pyrolysis of homogeneous lithium-cobalt-citrate precursors. Atomic scale mixing of Li and Co is achieved by citric acid acting as a chelating agent. Electron spectroscopy of concentrated Li-Co-citrate solutions with Li:Co:Cit=1:1:1 and Li:Co:Cit=1:1:2 reveals that the predominant species at pH=7 are [Co(C₆H₅O₇)]⁻ and [Co(C₆H₅O₇)₂]⁴⁻ complexes. Freeze-drying of the two types of solutions leads to the formation of LiCo(C₆H₅O₇).nH₂O and (NH₄)₃LiCo(C₆H₅O₇)₂.nH₂O precursors, where Co²⁺ ions are complexed by one and two triionized citrate ions, respectively, and Li⁺ ions serve as counter ions. Between 400–600 °C, the thermal decomposition of these metal-citrate precursors yields LiCoO₂ with layered and pseudo-spinel structure, the proportion between them being depending on: (i) the Co/citrate ratio; (ii) the concentration of the freeze-dried solution; (iii) the heating rate. At 400 °C, the most defectless layered LiCoO₂, consisting of hexagonal individual particles with dimensions of 120–170 nm, is a product of the bis-citrate decomposition with a slow heating rate. For this sample, heating up to 600 °C does not affect the crystal size dimensions. For ultrafine layered LiCoO₂ and LiCoO₂ obtained by solid state reaction at high-temperatures (850 °C), the deintercalation and intercalation reactions proceed in the 3.95 – 3.99 and 3.86 – 3.88 voltage intervals, respectively. For defect trigonal LiCoO₂, additional oxidation and reduction peaks at 3.7 – 3.8 and 3.4 – 3.5 V were observed. We did not succeed in preparing monophase LiCoO₂ with pseudo-spinel structure. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Sept. 14–21, 1996     

Evidence of nuclear motion in H<Subscript>2</Subscript>-like molecules by means of high harmonic generation

The dynamics of hydrogen-like molecules is investigated beyond the usual fixed nuclei approximation. The nuclear motion introduces in the familiar spectrum of emitted radiation additional regular lines whose separation is essentially given by the vibrational frequency of nuclear motion. A wavelet analysis of the emitted spectrum shows that the intensity of the harmonic lines is modulated with the same period of the nuclear motion; this suggests the possibility of the real-time control of the nuclear dynamics.     

Stimulated bremestrahlung in the presence of a high-intensity radiation field

Summary The theoretical treatment is given for the case when the emission or absorption of a weak-fied photon of arbitrary frequency ω₁ during a scattering process takes places in the presence of a strong laser field. The general formulation of the theory which is given in detail corresponds more properly to the case when an electron is scattered by a static potential in the presence of two arbitrary radiation fields. Part of theory is expected to cover also the process of the stimulated bremsstrahlung. A selected set of calculations is performed in the first order in the scattering potential for the case when one of the two fields is weak. The effects of the two fields are always treated exactly. The chosen geometry is the parallel one, in which the two linearly polarized fields are parallel to the initial electron velocity. The presence of a strong assisting field is found to yield several significant modification of the characteristics of emission/absorption of a weak-field photon. In paritcular, i) the final electron energy distribution is drastically altered; ii) angular distributions and total cross-sections of emission and absorption are modified up to become largely similar; iii) when the oscillatory velocityv ₀ is approximately equal to the incoming velocityv _i, the cross-sections experience rapid variations, generally in the sense of the growth; iv) for higher intensities, whenv ₀>v _i the strong field is found instead to dump considerably all the cross-sections, besides making emission and absorption similar. Accordingly, in the high-intensity domain, the question whether or not emissions prevail over absorptions looses part of its importance. In general, calculation shows that the quantities, accounting for the balance between emission and absorption, exhibit strong oscillations above and below zero either as a function of the strong-field intensity or as a function of the weak-field frequency.

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Riassunto Si propone un trattamento teorico per i processi di emissione e assorbimento di un fotone di campo debole a frequenza arbitraria ω₁ durante un processo di scattering in presenza di un forte campo laser. La formulazione generale della teoria è data in dettaglio relativamente al caso di un elettrone diffuso da un potenziale statico in presenza di due campi di radiazione di intensità arbitraria. La teoria sviluppata, è applicabile anche alla descrizione del processo di bremsstrahlung stimolato. Si presenta un gruppo di risultati ottenuti con una teoria al primo ordine nel potenziale statico, per il caso in cui uno dei due campi è debole. Gli effetti dei due campi sono trattati sempre in modo esatto. I risultati mostrano che la presenza di un forte campo laser è responsabile di numerose importanti modifiche delle caratteristiche dei processi di emissione/assorbimento di un fotone di campo debole. In particolare i) viene alterata drasticamente la distribuzione dell'energia finale degli elettroni; ii) le distribuzioni angolari e le sezioni d'urto totali d'emissione e assorbimento sono modificate fino a divenire largamente simili; iii) quando l'ampiezza della velocità di oscillazionev ₀ è approssimativamente uguale alla velocità di incidenzav _i , le sezioni d'urto subiscono rapide variazioni, generalmente nel senso della crescita; iv) per intensità piú elevate, quandov ₀>v _i , si trova che il campo spettatore riduce sensibilmente le sezioni d'urto, oltre a renderle simili. Di conseguenza, nel dominio delle alte intensità, la questione della prevalenza dell'emissione sopra l'assorbimento perde parte della sua importanza. In generale, il calcolo mostra che le quantità fisiche, che rendono conto del bilancio fra emissione e assorbimento, presentano un andamento oscillatorio, sopra e sotto lo zero, sia come funzioni dell'intensità del campo forte sia come funzioni della frequenza del campo debole.

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Резюме Теоретически рассматривается случай, когда излучение или поглощение фотона слабого поля произвольной частоты ω₁ в процессе рассеяния происходит в присутствии сильного лазерного поля. Предлагается общая формулировка теории, которая соответствует случаю, когда электрон рассеивается на статическом потенциале в присутствиии двух произволных радиационных полей. Часть теории описывает процесс стимулированного тормозного излучения. Проводятся вычисления в первом порядке по потенциалу рассеяния, когда одно из двух полей является слабым. Влияния двух полей всегда рассматривается точно. Выбранная геометрия соответствует случаю, когда два линейно поляризованных поля являются параллельными первоначальной скорости электрона. Обнаружено, что наличие дополнительнго поля приводит к существенному изменению характеристик излучения (или поглощения) фотона слабого поля. В частности: 1) существенно изменяется конечное энергетическое распределение электрона; 2) изменяются угловые распределения и полные поперечные сечения излучения и поглощения и становатся похожими; 3) когда осцилляторная скоростьv ₀ приближенно равна скорости налетающего электронаv _i поперечные сечения испытывают сильные изменения; 4) для высоких интенсивостей, когдаv ₀>v _i , отмечают значительное уменьшение поперечных сечений. В области высоких интенсивностей важным становится вопрос о том, превалируют ли процессы излучения над процессами поглощения или нет. В общем случае вычисления показывают, что величина, определяющая баланс между излучением и поглощением, обнаруживает сильные осцилляции выше и ниже нуля в зависимости от интенсивности поля или в зависимости от частоты слабого поля.

     

Crystallite size and microstrains of Co3O4 derived from CoOOH and Co(OH)2

The variation of crystallite size and microstrains in Co₃O₄ derived from the thermal decomposition of CoOOH and Co(OH)₂ is studied by X-ray diffraction line broadening analysis in several crystallographic directions. The results show that the low-temperature oxide derived from CoOOH produces lower crystallite size and microstrains, due to the development of cracks in the particles instead of a porous system which is characteristic of the sample derived from Co(OH)₂. On the other hand, microstrains decrease and crystallite size increases with temperature for both parent compounds, but the changes are dependent on the crystallographic direction. The shape of crystallites is anisotropic at low temperature but the isotropy increases on heating, specially for the samples obtained from CoOOH.     

Parity conserving weak neutral current effects in fundamental bound systems

The effects induced by the Z-boson exchange in the hyperfine structure and Lamb shift of some fundamental bound systems is analyzed. The hfs of muonium appears as a promising test of the Weinberg-Salam theiry.