Two-wavelength differential thermometry for microscopic extended source

Sample temperature may theoretically be determined if we know or measure four quantities (two radiances at two specific wavelengths). We performed differential, continuous two-wavelength thermometry on a micro-surface element of the coiled coil filament used in tungsten lamp with a spectrometer. Results indicate that differential, continuous thermometry using a spectrometer measures temperature distribution along a short line. This method significantly enhances the capability of this established technique to new applications.     

Gap-anisotropic model for the narrow-Gap kondo insulators

A theory is presented which accounts for the dynamical generation of a hybridization gap with nodes in the Kondo insulating materials CeNiSn and CeRhSb. We show that Hund's interactions acting on virtual 4f(2) configurations of the cerium ion can act to dynamically select the shape of the cerium ion by generating a Weiss field which couples to the shape of the ion. In low symmetry crystals where the external crystal fields are negligible, this process selects a nodal Kondo semimetal state as the lowest energy configuration.     

Mixed exponential sums over finite fields

In this paper we calculate the conductor of a character that consists of the product of an additive and a multiplicative character. This computation improves the bound for exponential sums given by G. I. Perelmuter. This calculation gives an easy method to compute the conductor associated to a character of the Galois group of the composite of an Artin-Schreier extension and a Kummer extension.

     

Intersite coupling effects in a kondo lattice

The La dilution of the Kondo lattice CeCoIn5 is studied. The scaling laws found for the magnetic susceptibility and the specific heat reveal two well-separated energy scales, corresponding to the single-impurity Kondo temperature T(K) and an intersite spin-liquid temperature T(*). The Ce-dilute alloy has the expected Fermi liquid ground state, while the specific heat and resistivity in the dense Kondo regime exhibit non-Fermi-liquid behavior, which scales with T(*). These observations indicate that the screening of the magnetic moments in the lattice involves antiferromagnetic intersite correlations with a larger energy scale in comparison with the Kondo impurity case.     

Sesquiterpenic acids from Leucanthemopsispulverulenta

From Leucanthemopsis pulverulenta (Compositae) ten new sesquiterpenic acids have been isolated. Their structures and absolute stereochemistry were assigned by spectral and chemical evidence; they are the first carboxylic acid members of the cadinane and munrolane series to be found in a natural source.     

Observations of backstreaming protons in the solar wind near the Earth's bow shock

Summary Protons backstreaming in the solar wind, upstream of the Earth's bow shock, are frequently revealed by the plasma, experiment on board satellite ISEE 2. Preliminary results of a statistical analysis (based on 479 ion energy spectra recorded in the period November 8 to 22, 1977) indicate that 1) the relative abundance of the backstreaming protons with respect to solar-wind protons is, on the average, ≲1%; 2) the bulk velocity of the backstreaming protons is, on the average, about twice the solar-wind velocity; 3) some backstreamingproton energy spectra are characterized by the presence of a dominant peak, localized in energy, while others consist of a very flat distribution extending up to at least 11 keV.

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Riassunto L'esperimento di vento solare, montato a bordo del, satellite ISEE 2, ha fornito l'opportunità di osservare freqeuntemente, nel vento solare, protoni riflessi dall'onda d'urto terrestre. I risultati preliminari di un'analisi statistica basata su 479 spettri energetici rilevati nel periodo di tempo compreso tra 1'8 e il 22 Novembre 1977 indicano che 1) l'abbondanza dei protoni riflessi dall'onda d'urto terrestre rispetto a quella dei protoni del vento solare è, in media, ≲1%; 2) la velocità d'insieme dei protoni riflessi è, in media, circa due volte quella del vento solare; 3) alcuni spettri energetici dei protoni riflessi sono caratterizzati dalla presenza di un picco dominante, mentre altri consistono di una distribuzione quasi uniforme che si estende fino al limite superiore di misura dello strumento che è pari a 11 keV/Z.

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Резюме ПротонЫ, направленнЫе в противоположную сторону, в солнечном ветре бЫли обнаруженЫ в результате плазменного эксперимента на борту спутника ISEE 2. ПредварительнЫе результатЫ статистического анализа (основанного на 479 энергетических спектрах ионов, зарегистрированнЫх в период с 8 по 22 ноября 1977 г.) указЫвают, что: 1) относительное увеличение протонов, направленнЫх в противоположную сторону по отношению к протонам солнечного ветра, в среднем, составляет ≲1%; 2) обьемная скорость таких протонов, в среднем, вдвое превЫшает скорость ветра; 3)некоторЫе энергетические спектрЫ протнов, направленнЫх в противоположную сторону, характеризуются наличием доминантного пика, локализовнного по энергии, тогда как другие спектрЫ представляют очень плавнЫе распределения, простирающиеся вплоть до 11 кэВ.

     

Evaluation and correction of aberrations in an optical correlator by phase-shifting interferometry

We propose a new method for evaluating and correcting aberrations in a Vander Lugt correlator. The technique is achieved with liquid-crystal displays of the correlator and allows the task to be performed in situ. We present the theory on which the method is based and the experimental results that we obtained by applying it in a convergent correlator.     

Analytical performance of an optical pH sensor for acid-base titration

The analytical performance of a reflectance optical fibre sensor is described for the determination of pH, particularly that of acid-base titration end-points. The sensor makes use of cresol red immobilized on the anion-exchange resin Dowex 1-X10, has a pH transition interval in the range 5.5–7.5 and uses a PTFE membrane as interface. The sensor r.s.d. is ca. 1% and the accuracy is excellent. It is useful for titrating strong and weak acids (such as HF) with bases and vice versa, and requires very small sample volumes. The sensor can titrate turbid and coloured solutions at different temperatures. The minimum response time necessary after each titrant addition is in the range 0.5–1 min.