Comparison between the impedance spectra of Li/SOCl2 batteries obtained using the time and the frequency domain measurement techniques

A comparison between the impedance spectra of Li/SOCl₂ batteries obtained in the time and frequency domains is reported. It is demonstrated that by averaging over several responses the accuracy in the time domain is greatly improved. On the other hand, it was found that the time domain technique caused nonlinearity in the system response even at very small amplitudes of excitation (for example corresponding to a potential drop of 30 mV). The method is useful for routine characterization of the quality of galvanic cells in industrial production. The accuracy compared with market-available impedance spectrometers operating in the frequency domain is satisfactory (±10%), the price being much lower.Nomenclature g _i parameters of model frequency response - g _id parametersg _i obtained by deconvolution - g _ir parametersg _i obtained by frequency domain method - H frequency response - H _m model frequency response - H _r reference frequency response - i(t) excitation current - I() Fourier transform of thei(t) - Im imaginary part - j imaginary unit - M Number of independent measurements - N number of samples - Re real part - R resistance - R ₀ ohmic resistance - T sampling time - u(t) response voltage - U() Fourier transform ofu(t) - dispersion factor - angular frequency - () phase spectrum - _a relative amplitude error - _gi relative error ofg _i - average relative amplitude error - _p relative phase error - average relative phase error - ₀ mean relaxation time     

Interfacial polymerization of pyrrole and in situ synthesis of polypyrrole/silver nanocomposites

We present a new synthetic approach leading to the formation of polypyrrole architectures in submicron level and to silver/polypyrrole nanocomposites via an interfacial polymerization in a water/chloroform interface. The oxidizing agent was either Ag(I) or Fe(III). In the first case, silver nanoparticles resulted. The mean diameter of the polypyrrole structures is in the range of 200-300 nm according to the addition or not of various surfactants. The progress of the reaction was studied by UV-visible spectroscopy, which also revealed the formation of a polaron band during the growth of the oligomers. The crystal structure of the polymers was examined by X ray diffractometry and all samples appeared to be amorphous, while the samples were further characterized by thermogravimetric analysis and FT-IR spectroscopy.     

Cellulose as a binding material in graphitic anodes for Li ion batteries: a performance and degradation study

Four types of cellulose, in particular carboxy methyl cellulose (CMC), are tested as potential binding materials in graphitic anodes for lithium ion batteries. It is shown that a minimum content of a cellulose which gives acceptable anode properties (reversible capacity>300 mA h g⁻¹ during the first 10 cycles, irreversible loss<20%) is about 2 wt.%, which is less than in the case of conventional polymeric binders (5-10 wt.%). Kinetics of insertion-deinsertion and passivation processes seem not to be affected by the presence of cellulose. Explanation for the electrode failure at cellulose contents lower than 1 wt.% is given based on X-ray diffraction and microscopy investigations. Finally, the structure (distribution) of cellulose in the composite anode material is discussed and (indirectly) checked with a series of experiments. Most results are compared with the corresponding results obtained either with gelatin or conventional polymeric binders or both.     

Electrochemical characterization of lithium-boron composite

Electrochemical measurements, including a.c. and d.c. techniques, were performed in order to determine the differences between Li-B alloy prepared at 600°C and Li-B composite prepared at 450°C. Li-B composites can be defined as very finely-grained, physically dispersed amorphous boron, entrapped in polycrystalline metallic lithium. SEM analysis of electrode surfaces, corroborating the electrochemical measurements, is given. Some experimental problems arising from passive layer formation on lithium in organic electrolytes which influence the reliability and reproducibility of the results are discussed.     

The compressibility and compactibility of different types of lactose

Objective: The purpose of this study was to investigate and quantify flow properties, compressibility, and compactibility of various pharmaceutical lactose powders found on the market today (DCL-11, DCL-21, M‐200, Flowlac-100, and Tablettose 70, 80, and 100). Methods: Flow properties were estimated by measuring flow time, angle of repose, and the Hausner ratio. Particle rearrangement was studied using Kawakita's linear model. Compressibility was studied using two ‘out-of-die’ methods: (i) the Heckel model and (ii) a modified Walker model. Compactibility was quantified using two methods: (i) the tensile strength profile (Cp) and (ii) the compactibility factor (Pr). Statistical approach was used to analyze the results. Results: Flow properties of all materials were passable or better, except for M-200, which has very poor flowability. Compressibility results demonstrated that the most compressible lactose is spray-dried grade of lactose (Flowlac-100) and the least compressible is milled lactose (M-200). Compactibility studies showed that β‐lactose (DCL-21) forms tablets with superior tensile strength in comparison with α-lactose. Conclusion: Results of the compressibility study showed that the discriminative power of modified Walker model is greater in comparison with Heckel model. Compactibility methods yield similar and comparable results.     

Electrochemical binding and wiring in battery materials

Binders in battery electrodes not only provide mechanical cohesiveness during battery operation but can also affect the electrode properties via the surface modification. Using atomic force microscopy (AFM), we study the surface structuring of three binders: polyvinylidene fluoride (PVdF), carboxymethyl cellulose (CMC) and gelatin. We try to find correlation between the observed structures and the measured electrochemical charge–discharge characteristics. We further measure the binding ability of gelatin adsorbed from solutions of different pHs. While the best binding ability of gelatin is obtained at pH about 9, the least polarization is observed at pH 12. Both properties are explained based on the observed gelatin structuring as a function of pH. In the second part of this study, gelatin is used as a surface agent that dictates the organization of nanometre-sized carbon black particles around micrometre-sized cathodic active particles. Using microcontact impedance measurements on polished pellets we show that using gelatin-forced carbon black deposition the average electronic resistance around LiMn₂O₄ particles is decreased by more than two orders of magnitude. We believe that it is this decrease in resistance that improves significantly the rate performance of various cathode materials, such as LiMn₂O₄ and LiCoO₂.     

Das Rotwild Jugoslawiens

Zusammenfassung Der Bestand an Rotwild in Jugoslawien wird Ende 1957 auf ca. 15000 Stück geschätzt. Wegen der mannigfaltigen geschichtlichen, geographischen, ökologischen und genetischen Faktoren, die auf das Rotwild in den verschiedenen Gebieten einwirkten, ist das Rotwild Jugoslawiens hinsichtlich des Phäno- und Genotyps sehr verschiedenartig.Zur Zeit steht fast das ganze Rotwild nördlich der Linie, die von den Flüssen Donau-Sava-Una gebildet wird, obwohl es ehemals fast auf dem ganzen Gebiet Jugoslawiens vorkam.Das jugoslawische Rotwild ist teilweise autochthon, zum Teil stammt es von Rotwild ab, das aus verschiedenen europäischen Staaten nach Jugoslawien, größtenteils Ende des 19. und zu Beginn des 20. Jahrhunderts, eingeführt wurde. Im Südosten herrscht der maraloide, ansonsten jedoch der hypelaphoide Geweihtyp vor.Das Rotwild Jugoslawiens ist gut. Hirsche erreichen Gewichte von 350 kg, Tiere von 180 kg. Viele Trophäen haben Gewichte über 10 kg und Punktzahlen über 200 der internationalen Madrider Formel. Der bisher stärkste erlegte Hirsch erzielte 248,5 Punkte und war 1954 Champion auf der Internationalen Jagdausstellung in Düsseldorf.

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Summary The number of red deer in Yugoslavia at the end of 1957 is estimated at approximately 15000 head. Because of widely differing historical, geographical, ecological and genetic factors, which have exercised, and are still exercising, their effect upon red deer in the various regions, this game differs in phenotype and genotype in Yugoslavia very much.At present almost all the red deer live north of the line formed by the rivers Danube, Sava, and Una, although in the past they were found practically throughout the whole of Yugoslavia.Yugoslav red deer are in part native to the country, and in part descended from red deer imported from various other European countries into Yugoslavia, mainly at the end 19th and the beginning of the 20th century. As regards type, the maraloid prevails towards the southeast, and the hypelaphoid type on the whole.Yugoslav red deer are an excellent breed. Many hunting trophies weight more than 20 lbs, and can claim more than 200 points according to the international Madrid formula. The most powerful stag shot so far was awarded 248,5 points and was the champion at the International Sportmen's (Hunters') Exhibition at Düsseldorf in 1954. The maximum weight attained by a stag is 350 kg (7 cwt.), and that of a hind 180 kg (3 1/2 cwt.).

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Résumé Le nombre des cerfs en Yougoslavie à la fin de l'année 1957 était 15 000 envinon. En conséquence des influences très différentes des facteurs historiques, géyographique, écologique et génétiques, qui se manifestaient et se manifestent dans les diverses régions, sont les cerfs de la Yougoslavie différents de points de vue phéno et génotypique.Presque tous les cerfs vivent au Nord de la ligne tracée par les riviéres de Danube, Save et Une, bien qu'ils vivaient jadis sur le territoire presqu' entier de la Yougoslavie.Une partie des cerfs de Yougoslavie sont autochthones, l'autre tire son origine des cerfs, qui étaient importés en Yougoslavie d'autres pays Européens, par la plupart vers la fin du 19^me et on début du 20^m3 siecle. Comme types, c'est le type maraloide qui domine au Sud-Est, ailleurs c'est le type hypélaphoide.Les cerfs de Yougoslavie sont de bonne qualité. Bien de trophées atteignent plus de 10 kg du poidset plus de 200 points (formule internationale de Madrid). Le plus fort parmis les cerfs tirés était le champion de l'Exposition intérnationale de chasse à Düsseldorf en 1954 ayant reçu 248,5 points. Les cerfs atteignent au maximum 350 kg et les biches 180 kg du poids.

     

Internalization and Accumulation in Dendritic Cells of a Small pH‐Activatable Glycomimetic Fluorescent Probe as Revealed by Spectral Detection

DC‐SIGN, an antigen‐uptake receptor in dendritic cells (DCs), has a clear role in the immune response but, conversely, can also facilitate infection by providing entry of pathogens into DCs. The key action in both processes is internalization into acidic endosomes and lysosomes. Molecular probes that bind to DC‐SIGN could thus provide a useful tool to study internalization and constitute potential antagonists against pathogens. So far, only large molecules have been used to directly observe DC‐SIGN‐mediated internalization into DCs by fluorescence visualization. We designed and synthesized an appropriate small glycomimetic probe. Two particular properties of the probe were exploited: activation in a low‐pH environment and an aggregation‐induced spectral shift. Our results indicate that small glycomimetic molecules could compete with antigen/pathogen for binding not only outside but also inside the DC, thus preventing the harmful action of pathogens that are able to intrude into DCs, for example, HIV‐1.     

The effect of pyridine ring functionalization on the conductivity of crosslinked CO-poly(styrene-4-vinylpyridine) derivatives

The effect of pyridine ring functionalization in crosslinked co-poly(styrene-4-vinylpyridine) on electrochemical behavior was studied using impedance spectroscopy. The introduction of a substituent on the nitrogen atom increases conductivity from 10^-14 to around 10^-11 Scm^-1 at room temperature, but the effect of the substituent becomes more evident at 64°C, at which the n-butyl derivative (co-poly[styrene-[4-vinyl(N-butylpyridinium bromide)]])-(3) has a higher conductivity (ω = 7 × 10⁻¹⁰ Scm⁻¹) than the hydrogen analog (co-poly[styrene-[4-vinyl(pyridinium bromide)]])-(2) (ω = 4.3 × 10⁻¹⁰ Scm⁻¹), while the iodo derivative (co-poly[styrene-[4-vinyl(N-iodopyridinium bromide)]])-(6) has a conductivity ten times lower. Further increase in the conductivity was observed upon the substitution of the bromine anion with the three-bromide anion (Br₃)⁻, but the effect depends on the substituent on the nitrogen atom: 4.4 times higher conductivity was found for the hydrogen pyridinium salt (4) in comparison with sample (2), and the conductivity increases 30-fold for the N-butyl derivative (5) compared with sample (3). The conductivity increased exponentially with temperature and the activation energy values vary from 0.76 to 1.01 eV. Impedance responses for dried samples of pyridinium salts (2), (3), (4), (5), and (6) suggested electron-type conductivity. The conductivity of crosslinked polymers depends very much on the conditions, and increases by several orders of magnitude when water or methanol is present in the atmosphere during measurement. The conductivity also depends on the structure of the substituent attached to the nitrogen atom: ω = 5 × 10⁻⁴ Scm⁻¹ and ω = 2 × 10⁻⁴ Scm⁻¹ for hydrogen bromide (2) and N-butyl bromide derivative (3), but the conductivity of the N-iodo derivative (6) changed very little. In contrast, the impedance responses for samples stored in the presence of water or methanol suggested ion conductivity. © 1996 John Wiley & Sons, Inc.