The ratio of diffusion coefficient to mobility for slow electrons in dry air

Using Huxley's solution of the diffusion equation for electron-attaching gases, the ratio of diffusion coefficient D to mobility μ for electrons in dry air was measured over the range 3·06 × 10-17

Voittoa tavoittelemattoman organisaation brandin rakentaminen. Case Slow Food

Tämän pro gradu-tutkielman tavoitteena oli kartoittaa voittoa tavoittelemattoman Slow Food-organisaation brandiin liitettyjä mielikuvia ja niitä tekijöitä, joilla brandin tavoitekuvaa tulisi jatkossa rakentaa. Koska nykyisin brandi ei ole enää pelkkien liikeyritysten yksityisomaisuutta, tutkimuksen teoreettinen asemointi perustui yhtäältä organisaation tunnettuuden kasvattamiseen brandin rakentamisen avulla ja toisaalta voittoa tavoittelemattoman toimintaympäristön erityispiirteiden näkökulmaan. Case-osion avulla haluttiin tarkastella globalisaation ja elintarviketalouden keskittymiselle vaihtoehtoisen, paikallisuuteen perustuvan ruokajärjestelmän vaikutuksia, mahdollisuuksia ja haasteita. Tutkimuksen empiirinen osuus muodostui laadullisesta tapaustutkimuksesta, jonka kohteena oli Slow Food-organisaatio. Tutkimus suoritettiin haastattelemalla kahtatoista Slow Food-organisaation sidosryhmien edustajaa Italian Piemontessa henkilökohtaisin haastatteluin, joiden pohjana oli brandi identiteetin elementeistä luodut kaksi teemaa: mielleyhtymiin ja arvoväittämään liittyvät tekijät. Aineiston analysoinnissa käytettiin teemoittelua ja sisällönanalyysia. Tutkimuksen lähestymistapa oli abduktiivinen. Tulosten mukaan Slow Food-brandi identifioituu sidosryhmilleen ensisijaisesti luotettavan ruoan kautta, johon katsottiin kuuluvan aidot, puhtaat raaka-aineet ja paikallisesti tuotetun ja jalostamattoman ruoan hyvä jäljitettävyys. Myös tiettyyn paikkaan ja arvoihin sidottujen kokemusten ja odostusten täyttymisen kautta saatu sosiaalinen ja kulttuurinen jatkuvuus nimettiin brandin vahvuudeksi. Lisäksi vastuullisen tuottamisen ja kuluttamisen sekä aitojen makujen ja laadukkaan ruokavalion edistäminen korostuivat jonkin verran vastauksissa. Näillä perusvahvuuksilla toivottiin brandin identiteettiä rakennettavan myös tulevaisuudessa. Haastateltavien mielestä Slow Food-organisaatio erilaistaa itsensä muista ensisijaisesti lupaamalla yksilölle korkealuokkaisia, aitoja tuotteita ja palveluja, joilla on henkilökohtaisten hyötyjen lisäksi positiivisia seuraamuksia myös oman alueen työllisyyden ja talouden kehitykseen. Organisaation tulisi myös jatkossa luoda uskottavuutta toimintaansa eritoten sen kautta, että brandi lunastaa lupauksensa laadusta ja aitoudesta. Toisaalta erottautuakseen muista lähi- ja luomuruokabrandeista Slow Food-brandin arvoväittämässä tulisi tulevaisuudessa selkeämmin korostua myös toiminnan voittoa tavoittelemattomuus ja brandiin liittyvä elämyksellisyys. Sidosryhmien kiinnostusta ja brandin lupauksen tehoa alentaviksi tekijöiksi nimettiin yleinen ruoan arvostuksen väheneminen sekä Slow Food-tuotteiden ja -palvelujen korkea hinta, huono saatavuus ja näkyvyys. Keskeisimpinä ratkaisuina pidettiin kuluttajien informatiivisen tiedon lisäämisen ohella pientuottajien verkostoitumista ja uusia yhteistyön muotoja kuten tuottajien yhteisiä jakeluketjuja ja paikallismyymälöitä. Näiden lisäksi brandin tunnistettavuuden parantaminen ja aktiivisempi tarjonta kyltityksin, tuotteiden pysyvän läsnäolon ja vähittäiskaupan mukaantulon kautta sekä eräät muut markkinoinnin osa-alueet kuten sosiaalinen media, Internet ja kansainväliset ruoka-alan tapahtumat nimettiin brandin lupausta kirkastaviksi elementeiksi. Pientuotannon lisääminen verotuksen kohdentumisen muutoksilla nähtiin keinoksi pudottaa paikallisen ruoan hintaa.Toisaalta korkeaa hintaa perusteltiin laadukkaaseen imagoon liittyvien argumenttien lisäksi luonnollisen kysynnän kasvulla, jota arveltiin saatavan tulevaisuudessa suurista ikäluokista, yhä kasvavasta koulutus- ja tulotasosta sekä valveutuneemmista kuluttajista.

A study of the slow reaction in Al-5 wt.% Ag alloy by resistivity measurements

The slow reaction in an Al-5 wt.% Ag alloy has been investigated by resistivity measurements. The "slope change" method gave an activation energy of 1.25 eV for silver diffusion during the slow reaction. The existence of an excess concentration of vacancies in equilibrium with the dislocation loops seems to be responsible for the slow reaction. The presence of silver inhibits the nucleation of dislocation loops by holding up the quenched-in vacancies in solution. There is no indication of the presence of a third stage in the low-temperature ageing process of this alloy.

Dielectric relaxation and electrical conductivity in Bi5NbO10 oxygen ion conductors prepared by a modified sol–gel process

Crystalline Bi5NbO10 nanoparticles have been achieved through a modified sol–gel process using a mixture of ethylenediamine and ethanolamine as a solvent. The Bi5NbO10 nanoparticles were characterized by X-ray diffraction (XRD), differential scanning calorimetry/thermogravimetry (DSC/TG), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and Raman spectroscopy. The results showed that well-dispersed 5–60 nm Bi5NbO10 nanoparticles were prepared through heat-treating the precursor at 650 °C and the high density pellets were obtained at temperatures lower than those commonly employed. The frequency and temperature dependence of the dielectric constant and the electrical conductivity of the Bi5NbO10 solid solutions were investigated in the 0.1 Hz to 1 MHz frequency range. Two distinct relaxation mechanisms were observed in the plots of dielectric loss and the imaginary part of impedance (Z″) versus frequency in the temperature range of 200–350 °C. The dielectric constant and the loss in the low frequency regime were electrode dependent. The ionic conductivity of Bi5NbO10 solid solutions at 700 °C is 2.86 Ω−1 m−1 which is in same order of magnitude for Y2O3-stabilized ZrO2 ceramics at same temperature. These results suggest that Bi5NbO10 is a promising material for an oxygen ion conductor.

Vibrational force constant and electron relaxation in H2 and Li2

The force constants of H2 and Li2 are evaluated employing their extended Hartree-Fock wavefunctions by a polynomial fit of their force curves. It is suggested that, based on incomplete multiconfiguration Hartree-Fock wavefunctions, force constants calculated from the energy derivatives are numerically more accurate than those obtained from the derivatives of the Hellmann-Feynman forces. It is observed that electrons relax during the nuclear vibrations in such a fashion as to facilitate the nuclear motions.

NMR relaxation study of disorder in condensed matter: solid solutions of betaine phosphate and phosphite

Proton NMR relaxation measurements have been carried out in anti-ferroelectric Betaine phosphate (BP), ferroelectric Betaine phosphite (BPI) and the mixed system BPI(1-x)BPx, at 11.4MHz and 23.3MHz from 300K to 80K for x=0.0, 0.25, 0.45, 0.85, and 1.0. The temperature dependence of spin lattice relaxation time T, exhibits two minima as expected from the BPP model in BP and BPI. The Larmor frequency dependence of T, in the mixed system is rather unusual and exhibits different slopes for the low temperature wings at the two frequencies, which is a clear experimental evidence of the presence of different methyl groups with different activation energies (E-a) indicating disorder.

Temperature- and pressure-dependent study of Cl-35 NQR frequency and spin lattice relaxation time in 2,3-dichloroanisole

The temperature and pressure dependence of Cl-35 NQR frequency and spin lattice relaxation time (T-1) were investigated in 2,3-dichloroanisole. Two NQR signals were observed throughout the temperature and pressure range studied. T-1 were measured in the temperature range from 77 to 300 K and from atmospheric pressure to 5 kbar. Relaxation was found to be due to the torsional motion of the molecule and also reorientation f motion of the CH3 group. T-1 versus temperature data were analyzed on the basis of Woessner and Gutowsky model, and the activation energy for the reorientation of the CH3 group was estimated. The temperature dependence of the average torsional lifetimes of the molecules and the transition probabilities were also obtained. NQR frequency shows a nonlinear behavior with pressure, indicating both dynamic and static effects of pressure. The pressure coefficients were observed to be positive for both the lines. A thermodynamic analysis of the data was carried out to determine the constant volume temperature coefficients of the NQR frequency. The variation of spin lattice time with pressure was very small, showing that the relaxation is mainly due to the torsional motions of the molecules. Copyright (C) 2010 John Wiley & Sons, Ltd.

Fast versus slow response in climate change: implications for the global hydrological cycle

Recent studies have shown that changes in global mean precipitation are larger for solar forcing than for CO2 forcing of similar magnitude.In this paper, we use an atmospheric general circulation model to show that the differences originate from differing fast responses of the climate system. We estimate the adjusted radiative forcing and fast response using Hansen's ``fixed-SST forcing'' method.Total climate system response is calculated using mixed layer simulations using the same model. Our analysis shows that the fast response is almost 40% of the total response for few key variables like precipitation and evaporation. We further demonstrate that the hydrologic sensitivity, defined as the change in global mean precipitation per unit warming, is the same for the two forcings when the fast responses are excluded from the definition of hydrologic sensitivity, suggesting that the slow response (feedback) of the hydrological cycle is independent of the forcing mechanism. Based on our results, we recommend that the fast and slow response be compared separately in multi-model intercomparisons to discover and understand robust responses in hydrologic cycle. The significance of this study to geoengineering is discussed.

A molecular theory of collective orientational relaxation in pure and binary dipolar liquids

A molecular theory of collective orientational relaxation of dipolar molecules in a dense liquid is presented. Our work is based on a generalized, nonlinear, Smoluchowski equation (GSE) that includes the effects of intermolecular interactions through a mean‐field force term. The effects of translational motion of the liquid molecules on the orientational relaxation is also included self‐consistently in the GSE. Analytic expressions for the wave‐vector‐dependent orientational correlation functions are obtained for one component, pure liquid and also for binary mixtures. We find that for a dipolar liquid of spherical molecules, the correlation function ϕ(k,t) for l=1, where l is the rank of the spherical harmonics, is biexponential. At zero wave‐vector, one time constant becomes identical with the dielectric relaxation time of the polar liquid. The second time constant is the longitudinal relaxation time, but the contribution of this second component is small. We find that polar forces do not affect the higher order correlation functions (l>1) of spherical dipolar molecules in a linearized theory. The expression of ϕ(k,t) for a binary liquid is a sum of four exponential terms. We also find that the wave‐vector‐dependent relaxation times depend strongly on the microscopic structure of the dense liquid. At intermediate wave vectors, the translational diffusion greatly accelerates the rate of orientational relaxation. The present study indicates that one must pay proper attention to the microscopic structure of the liquid while treating the translational effects. An analysis of the nonlinear terms of the GSE is also presented. An interesting coupling between the number density fluctuation and the orientational fluctuation is uncovered.

Polarization relaxation, dielectric dispersion, and solvation dynamics in dense dipolar liquid

A unified treatment of polarization relaxation, dielectric dispersion and solvation dynamics in a dense, dipolar liquid is presented. It is shown that the information of solvent polarization relaxation that is obtained by macroscopic dielectric dispersion experiments is not sufficient to understand dynamics of solvation of a newly created ion or dipole. In solvation, a significant contribution comes from intermediate wave vector processes which depend critically on the short range (nearest‐neighbor) spatial and orientational order that are present in a dense, dipolar liquid. An analytic expression is obtained for the time dependent solvation energy that depends, in addition to the translational and rotational diffusion coefficients of the liquid, on the ratio of solute–solvent molecular sizes and on the microscopic structure of the polar liquid. Mean spherical approximation (MSA) theory is used to obtain numerical results for polarization relaxation, for wave vector and frequency dependent dielectric function and for time dependent solvation energy. We find that in the absence of translational contribution, the solvation of an ion is, in general, nonexponential. In this case, the short time decay is dominated by the longitudinal relaxation time but the long time decay is dominated by much slower large wave vector processes involving nearest‐neighbor molecules. The presence of a significant translational contribution drastically alters the decay behavior. Now, the long‐time behavior is given by the longitudinal relaxation time constant and the short time dynamics is controlled by the large wave vector processes. Thus, although the continuum model itself is conceptually wrong, a continuum model like result is recovered in the presence of a sizeable translational contribution. The continuum model result is also recovered in the limit of large solute to solvent size ratio. In the opposite limit of small solute size, the decay is markedly nonexponential (if the translational contribution is not very large) and a complete breakdown of the continuum model takes place. The significance of these results is discussed.

A soluble random-matrix model for relaxation in quantum systems

We study the relaxation of a degenerate two-level system interacting with a heat bath, assuming a random-matrix model for the system-bath interaction. For times larger than the duration of a collision and smaller than the Poincaré recurrence time, the survival probability of still finding the system at timet in the same state in which it was prepared att=0 is exactly calculated.

Dynamics of polar solvation: Route to single exponential relaxation via translational diffusion

A microscopic theoretical calculation of time-dependent solvation energy shows that the solvation of an ion or a dipole is dominated by a single relaxation time if the translational contribution to relaxation is significant.

Two-stage photoquenching in semi-insulating GaAs:EL2

The photoquenching of EL2 in semi‐insulating gallium arsenide is seen to be a complex process, where at low temperatures the initial slow quenching is followed by a switch to fast quenching. A possible explanation involving lattice strain mediated cooperative structural relaxation arising out of transition to the metastable state is proposed.