On the influence of superconductivity on the phonon frequencies in a two-band model

Summary The influence of the onset of hole pairing onq=0 phonon frequency in a two-band model of high-T _c superconductivity is investigated. The estimated frequency shifts indicate a phonon softening with the lowering of temperature and agree with the experimental magnitude.     

The role of davydov solitons in the molecular chains with cubic anharmonicity in the electron transfer from the donor to the acceptor molecule

Summary This paper is concerned with the study of electron transfer from a donor molecule (D) to an acceptor molecule (A) along a one-dimensional molecular chain to which D and A are joined. It is shown that, in the case when the chain vibrations are with cubic anharmonicity, the probability of electron transfer has analogous form as well as in a previous paper.

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Riassunto Questo lavoro tratta lo studio del trasferimento degli elettroni da una molecola donatrice (D) a una molecola ricevente (A) lungo una catena molecolare unidimensionale alla quale sono unite D e A. Si mostra che, nel caso in cui le vibrazioni della catena avvengano con anarmonicità cubica, la probabilità di trasferimento elettronico ha forma analoga a quella trattata in precedenza.

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Резюме В этой статье исследуется перенос электрона от донорной молекулы (D) к акцепторной молекуле (А) вдоль одномерной молекулярной цепочки, в которой объединены молекулы D и А. Показывается, что в случае, когда колебания цепочки обладают кубческой ангармоничностью, то вероятность переноса электрона имеет аналогичную форму, также как и в предыдущей статье.

     

Feasibility of model ecosystems

Summary We introduce a structure with preferential trophic channels in a two-level Lotka-Volterra model. We discuss the dependence of feasibility on the number of species and on other properties of the system.

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Riassunto S'introduce una struttura con canali trofici preferenziali in un modello di Lotka-Volterra a due livelli. Si discute la dipendenza della realizzabilità del modello dal numero di specie e da altre proprietà del sistema.

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Резюме В двухуровневую модель Лотки-Вольтерра вводится структура с предпочтительными трофическими каналами. Мы обсуждаем влияние числа видов и других свойств системы на реализуемость модели.

     

On the possibility of nonequilibrium high-temperature superconductivity in PdH and PdD

Summary The possibility of acoustic plasmons leading to nonequilibrium high-temperature superconductivity is considered in the system Pd-H(D). The author of this paper has agreed to not receive the proofs for correction.     

Gauge-invariant treatment of the exponential decay of an unstable atomic state

Summary By using a self-consistent projection-operator method, developed recently by the present author, a gauge-invariant Markovian treatment of the spontaneous decay of an unstable atomic state is presented. Without ignoring retardation and electron-spin effects a gauge-invariant result for the probability amplitude of finding the atom in the unstable state is obtained.     

Diagonalization of the elliptic Ruijsenaars model. Correspondence with the Belavin model

Studied is the elliptic Ruijsenaars model, which is a difference analogue of the Calogero-Sutherland-Moser model. Using a novel relationship between the elliptic Ruijsenaars operator and the transfer matrix of the Belavin model, we diagonalize the Ruijsenaars operator by the algebraic Bethe ansatz method. Received: 29 January 1998 / Accepted: 17 April 1998     

Investigation on the chirality of positrons from22Na decay and their asymmetrical interactions with D-, L- and DL-alanines

Summary An investigation on the chirality of the positrons from²²Na and on their asymmetrical interactions with D-, L-, and DL-alanines was carried out. By using nuclear gamma-spectroscopy, the asymmetrical interaction was proved to be induced with a distinguishably asymmetrical effect.

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Riassunto è stata studiata l'interazione di positroni polarizzati con aminoacidi, D- L- e DL-alanine. Mediante misure di spettrometria nucleare gamma, si dimostra che l'interazione è asimmetrica e l'entità di tale effetto asimmetrico viene quantificata.

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Резюме Исследуются киральнсоть позитронов из распада²²Na и их асимметричные взаимодействия с D-, L- и DL-аланинами. Используя ядерную гаммаспектроскопию, доказывается, что асимметричное взаимодействие индуцирует асимметричный зффект.

     

On the instability of ionospheric plasma originated by charge separations in the troposphere. The «UFO» phenomenon mechanism

Summary The troposphere is the seat of powerful processes which originate separation of electric charges. Thunder clouds give rise to a huge vertical separation of charges. But also known is a different electrification mechanism activated by wind, which allows for horizontal separation of charges. In favourable conditions, when charges are displaced at long distances, image charges appear in the ionspheric plasma and an upward electric field is originated which makes the ionosphere boundary unstable. If this occurs, recombination of displaced charges involves ionosphere conductivity and gives rise to a downward electron stream ejected from the bottom of the ionosphere. It may produce a peculiar airglow phenomenon, which consists of the emission of light in a narrow region lying at stratospheric or mesospheric altitudes. This outcome of the electrification process just mentioned shows a close connection with a special class of ?UFO? sightings, that is, those referred to by J. Hynek as ?nocturnal light? and which consist of bright specks of light moving in the night sky.     

Dielectric and anharmonic behaviour of mixed alkali halides

Summary In the present paper an analysis of the dielectric behaviour and anharmonic contribution to the dielectric constants has been made of KCl−KBr mixed ionic crystals. The temperature and volume derivatives of static (ε₀), electronic (ε_∞) dielectric constants and energy gap parameter (E _g) have been calculated using the Szigeti and Havinga and Bosman dielectric theories. The anharmonic contributions have been estimated in terms of temperature derivatives of dielectric constants at constant volumes. The modified form of Clausius-Mossotti theory of dielectric polarization has been used for the mixed crystal under study. The calculated quantities have been compared with the available experimental data. A good agreement has been obtained. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Dielectric and thermoelastic properties of alkaline-earth fluoride crystals

Summary An extended three-body force shell model is developed and used to make an analysis of the volume dependence of low- and high-frequency dielectric constants and thermoelastic Grüneisen parameters for CaF₂, SrF₂, BaF₂ and PbF₂ crystals. Lorentz-Lorenz and Clausius-Mossotti relations are modified in view of three-body interactions (TBI). Calculated results yield better agreement with the experimental data as compared to those obtained by previous investigators.

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Riassunto Si sviluppa un modello esteso a strati della forza a tre corpi e se ne fa uso per un'analisi della dipendenza dal volume delle costanti dielettriche a bassa e alta frequenza e dei parametri termoelastici di Grüneisen per cristalli di CaF₂, SrF₂, BaF₂ e PbF₂. Si modificano le relazioni di Lorentz-Lorenz e di Clausius-Mossotti in vista delle interazioni a tre corpi (TBI). I risultati calcolati sono in migliore accordo con i dati sperimentali di quelli ottenuti da precedenti studi.

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Резюме Предлагается оболочечная модель для протяженной трех-частичной силы. эта модель используется для анализа обьемной зависимости при низких и высоких частотах диэлектрических постоянных и термо-упругих параметров Грюнайзена для кристаллов CaF₂, SrF₂, BaF₂ и PbF₂. Для трех-частичных взаимодействий модифицируются соотношения Лоренц-Лоренца и Клаузиуса-Москотти. Вычисленные результаты дают лучшее согласие с экспериментальными данными, чем результаты других авторов.

     

On some measurements of the propagation properties of thermal waves in the Nb-H and Ta-H systems

Summary By means of an experimental technique based on a nonsteady-state method,i.e. on the propagation of thermal waves, we have measured at room temperature for oscillation frequencies between 6 and 30 mHz the thermal diffusivity, the lateral thermal-loss coefficient and the ?fractional heat loss? in Nb and Ta wires as a function of hydrogen doping. The appearance of hydride formation and precipitation notably changes the behaviour of these quantities. From these measurements it was also possible to calculate the propagation velocity and attenuation coefficient of thermal waves. It was found that the increase of the hydrogen concentration in the solid solution produces a gradual decrease in the velocity and increase in the attenuation coefficient until the solubility limit is reached. For larger hydrogen concentrations, the velocity showed a tendency to increase towards the value of the pure metal, while the attenuation coefficient decreased below the value of the pure metal. These results as a whole appear quite promising for studying the properties of hydrogenated systems. This work was supported by the Gruppo Nazionale di Struttura della Materia of the Consiglio Nazionale delle Ricerche and by the Centro Interuniversitario di Struttura della Materia of the M.P.I., Roma (Italia).     

Mössbauer and ERS evidence of hemocromes in neoplastic pathologies

Summary Red blood cells collected from patients with leukaemia and breast cancer have been investigated with M?ssbauer spectroscopy. A component not usually present in red cells has been analysed. The M?ssbauer parameters, also supported by electron spin resonance measurements, suggest that they can be assigned to a hemocrome. This work was supported by Ministero Pubblica Istruzione and Italian National Research Council.     

Inclusion of retardation effects in the nonrelativistic treatment of the lamb shift

Summary The retardation effects are included in the nonrelativistic calculation of the Lamb shift, by using a method which exploits theO(4) symmetry of the nonrelativistic hydrogen atom. This method has been previously applied by Lieber to the treatment of the Lamb shift. However, in contrast to his calculations, no kind of dipole approximation, leading to the introduction of an inconsistent cut-off frequency, is used in our treatment. Apart from obtaining cut-off-independent results, the inclusion of retardation effects makes also possible the calculation of the spin-radiation-field Lamb-shift contribution (which vanishes in the dipole approximation). Furthermore, our unambiguous renormalization, consisting of removing the unobservable free-electron self-energy contribution from our expressions, leads to finite analytical and numerical results for the energy level (Lamb) shifts. The comparison of these results with those obtained in a nonrelativistic treatment by other authors shows that our results are in better agreement with the experiment.     

Experimental validation of a simulation code to describe the building thermal behaviour

Summary Room temperature trends have been measured in a small apartment in different climatic conditions. The results are compared with those evaluated through a recently reported simulation procedure which treats the building analytically by network theory.

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Riassunto Sono stati misurati gli andamenti della temperatura interna di un piccolo appartmento in varie condizioni meteorologiche. I valori cosí ottenuti sono stati confrontati con quelli previsti mediante un metodo di simulazione recentemente presentato in letteratura e che si basa su una trattazione analitica dell'edificio attraverso la teoria delle reti.

     

Analysis of the CO vibrational distribution obtained from formaldehyde laser photodecomposition

Summary A simple analysis of the overall CO vibrational distribution obtained from formaldehyde laser photodecomposition has been carried out. Extrapolation to zero vibrational energy transfer to CO gives an energy value of (27770±80) cm⁻¹ for the intermediate assumed in the formaldehyde predissociation. The result obtained turns out to be very reasonable and consistent with several mechanisms suggested in previous studies To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Density effects on the spectral intensities of dielectronic satellite line in dense plasmas

Summary In this paper we present a theoretical analysis of the spectral intensity of dielectronic satellite lines in dense plasmas. The ion microfield causes an oscillator strength mixing that alters the spectral intensity of such a transition. Numerical calculations of this high-density effect have been performed for the most intense 2l2l′→1s2l He-like transitions.

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Riassunto In questo articolo si presenta un'analisi teorica dell'intensità spettrale delle linee di satellite dielettroniche in plasmi densi. Il microcampo ionico causa un mescolamento delle forze dell'oscillatore che modifica l'intensità spettrale di una tale transizione. Si sono effettuati calcoli numerici di questo effetto ad alta densità per le transizioni più intense del tipo 2l2l′→1s2l.

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Резюме В этой работе мы предлагаем теоретический анализ спектральной интенсивности диэлектронных линий сателлитов в плотной плазме. Микрополе иона вызывает смешивание сил осцилляторов, что изменяет спектральную интенсивность такого перехода. Проведены численные вычисления эффекта высокой плотности для наиболее интенсивных Не-подобных переходов 2l2l′→1s2l.

     

Determination of the saturation parameter of electronic transition in a uranium-neon hollow-cathode discharge by optogalvanic spectroscopy

Summary The optogalvanic signal (OGS) induced in a uranium-neon hollow-cathode discharge was measured as a function of the laser power density for the 0→16900 cm⁻¹ (591.5 nm) uranium transition. Theoretical relations derived by solving a two-level system rate equations showed the OGS dependence on the laser photon flux, for a modulated c.w. light and for stimulated transitions starting from the ground state. A fitting of the theoretical relations to the experimental measurements allowed the determination of the σ₀ τ product, that is, the saturation parameter of the transition. The results showed good agreement between the σ₀ τ values obtained by the optogalvanic and the usual optical absorption processes.     

Energy balance of a climatized building: Comparison between simulation and experiment

Summary The heating energy required for the winter climatization of a small apartment has been measured; it results in good agreement with the figures obtained by a recently reported simulation procedure. The comparison with the usually adopted calculation code, which was taken as basis from the Italian standards, is discussed.

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Riassunto è stata misurata l'energia necessaria a garantire, nel periodo invernale, il mantenimento di una data temperatura all'interno di un piccolo appartamento; si è confrontato il risultato cosí ottenuto con quello previsto mediante un programma di simulatzione recentemente descritto. Si discute il confronto tra questi risultati e le previsioni delle procedure di calcolo usualmente adottate, su cui si basa, ad esempio, la normativa italiana per questo settore.

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Резюме Измеряется величина тепловой энергии, необходимой в зимний период для небольшой квартиры. Результаты хорошо согласуются с данными, полученными недавно с помощяю программы моделирования. Проводится сравнение полученных результатов с предсказаниями обычно применяемых вычислений, которые базируются на Итальянских стандартах.