Squid biomagnetic measurements

Nineteen years have elapsed since Baule and McFee¹ first recorded a biomagnetic field, that of the human heart. Progress during most of this time has been slow and the overall impact of biomagnetism is still small. However, a number of recent developments have demonstrated a research and clinical potential that has quickened interest in the area. A recent general review² and a comprehensive volume of research papers³ together provide an excellent overview of the whole field and we shall refer frequently to both of them. A brief introduction should serve to establish the specific focus of the present review.     

Flow rate measurements by means of tracers

Summary The application of some sources of diffusion for the flow rate measurement of water or other fluids is here presented. The laminar instantaneous source, obtained in practice with easy devices, is very useful in river or channel measurements. The analysis of the measurements could supply the flow rate and the presence of water losses or recharges. The section of the channel can also be determined by such a method.

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Riassunto Come traccianti per marcare le acque possono essere usate sostanze che diffondono secondo particolari geometrie. L'equazione della diffusione fornisce soluzioni diverse a seconda della geometria della sorgente. La sorgente laminare istantanea permette semplici soluzioni per la determinazione, con semplici iniezioni di sali, coloranti o sostanze radioattive, della portata di una corrente, della sua sezione ed anche della presenza di apporti e perdite occulte, si da permettere il bilancio idrologico più completo. La tecnica è assai raccomandabile per determinazioni su fiumi e canali, ma può essere usata, sfruttando opportuni traccianti naturali, anche per misure su correnti oceaniche.

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Резюме В работе описывается применеине некоторых источников диффузии для измерения интенсивности потоков воды или других жидкостей. Ламинарный мтновенный источник очень удобен при измерениях в реке или канале. Анализ измерений может дать интенсивность течения и наличие потерь воды или перезарядки. С помощью такого метода определяется также разрез канала.

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Publ. No. 182.     

Detecting and localizing the foci in human epileptic seizures

We consider the electrical signals recorded from a subdural array of electrodes placed on the pial surface of the brain for chronic evaluation of epileptic patients before surgical resection. A simple and computationally fast method to analyze the interictal phase synchrony between such electrodes is introduced and developed with the aim of detecting and localizing the foci of the epileptic seizures. We evaluate the method by comparing the results of surgery to the localization predicted here. We find an indication of good correspondence between the success or failure in the surgery and the agreement between our identification and the regions actually operated on.     

Mixed entanglement distillation by means of parity measurements

We present a mixed entanglement distillation protocol by means of the parity measurement of qubits. Without the use of controlled-NOT (CNOT) operations, the efficiency of our protocol can approach that of the CNOT protocol. In comparison, the total successful probability of our protocol can reach a quantity twice as large as that of the linear optics-based protocol.     

Refractive index distribution measurements by means of spectrally-resolved white-light interferometry

A new procedure to measure the spatial distribution of the refractive index in transparent media is presented. It is based on the spectral analysis of optical interferograms obtained from a wide, continuous-spectrum light source. The method yields fairly high precision (up to 10^-8) in the measurements of local values of differential refractive index, Δn (Δn=n−n_ref), along a line in the sample. By means of a CCD TV-camera linked to a microcomputer, fast recording and automatic data processing are achieved. As an application, we present an experimental study of a thermal gradient in a liquid sample.     

Enhancing teleportation fidelity by means of weak measurements or reversal

The enhancement of teleportation fidelity by weak measurement or quantum measurement reversal is investigated. One qubit of a maximally entangled state undergoes the amplitude damping, and the subsequent application of weak measurement or quantum measurement reversal could improve the teleportation fidelity beyond the classical region. The improvement could not be attributed to the increasing of entanglement, quantum discord, classical correlation or total correlation. We declare that it should be owed to the probabilistic nature of the method.     

Low-energy ion measurements by means of CR-39 nuclear track detectors

The paper presents an additional acceleration system, used to shift up an ion energy spectrum by 20 keV, and some examples of the ion parabolas registered by means of a Thomson-type spectrometer within the rod plasma injector (RPI-60) facility, designed for plasma physics and application studies. The use of the described acceleration system and CR-39 track detectors has enabled the registration of ions of energy above 20 keV to be performed. It made possible to measure the ion (e.g. deuteron) energy spectrum more exactly in the low-energy range, what is important for the determination of ion emission characteristics.     

Dynamical analogy between epileptic seizures and seismogenic electromagnetic emissions by means of nonextensive statistical mechanics

The field of study of complex systems considers that the dynamics of complex systems are founded on universal principles that may be used to describe a great variety of scientific and technological approaches of different types of natural, artificial, and social systems. Several authors have suggested that earthquake dynamics and neurodynamics can be analyzed within similar mathematical frameworks. Recently, authors have shown that a dynamical analogy supported by scale-free statistics exists between seizures and earthquakes, analyzing populations of different seizures and earthquakes, respectively. The purpose of this paper is to suggest a shift in emphasis from the large to the small scale: our analyses focus on a single epileptic seizure generation and the activation of a single fault (earthquake) and not on the statistics of sequences of different seizures and earthquakes. We apply the concepts of the nonextensive statistical physics to support the suggestion that a dynamical analogy exists between the two different extreme events, seizures and earthquakes. We also investigate the existence of such an analogy by means of scale-free statistics (the Gutenberg–Richter distribution of event sizes and the distribution of the waiting time until the next event). The performed analysis confirms the existence of a dynamic analogy between earthquakes and seizures, which moreover follow the dynamics of magnetic storms and solar flares.     

Localization of intracular and intraorbital foreign bodies by means of A-scan ultrasonography.

This paper discusses the use of ultrasonography in ophthalmology for foreign body localization and detection. The problems and advantages of using A-scann methods to verify and improve upon x-ray diagnosis are considered.     

Theory of electrical conductivity measurements in semiconductor films by means of probes

The authors derive general equations for the electrical conductivities of thin films from four-probe measurements. They discuss some special common cases.In conclusion, the authors wish to thank V. V. Postnikov and Yu. A. Romanov for discussion and valuable comments.     

On some measurements of thermal diffusivity by means of thermal-wave propagation in wires

Summary By means of a new experimental technique based on a non-steady-state method,i.e. on the propagation properties of thermal waves, we have measured the thermal diffusivityD of a copper wire by changing properly its boundary conditions in order to ascertain whether the values ofD were independent of the surface heat losses. Temperature oscillations at the fixed frequency of 0.0121 Hz were excited at one end of the specimen which was in nitrogen atmosphere at different pressures ranging from ∼10⁻² mTorr to 220 mTorr. The temperatures of the far end of the specimen and the walls of the container had the same constant value of 0°C, while the temperature gradient between the average value of the oscillating temperatures and this constant temperature was changed from 2°C to 12°C for each pressure by adjusting the heater power. By operating in this way it was possible to change either the heat losses due to conduction and convection or those due to radiation. The major cause of error came from the uncertainty in the measurements of the phase shift between the thermal oscillations detected at the two fixed points of the specimen which introduces in the evaluation ofD an error of about 2%. The experimental values obtained for the thermal diffusivity in these different boundary conditions were in any case comprised within this uncertainty sinceD=(1.17±0.02) cm²s⁻¹, in good agreement with the literature. The results so far obtained show that the experimental method has the great advantage of giving the thermal diffusivity and, therefore, the thermal conductivity of a solid without the necessity of taking particular care in insulating the specimen.

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Riassunto Utilizzando una tecnica sperimentale che consente di determinare in fili metallici sia la diffusività termicaD sia il coefficienteμ di perdita superficiale mediante la misura diretta del ritardo di fase e dell'attenuazione di un'onda termica tra due punti fissi del campione, ci si è proposti di analizzare alcuni risultati ottenuti recentemente in un campione di rame, variando opportuamente le condizioni al contorno. In particolare, ci si è voluti assicurare che la diffusività termica non risultasse dipendente dal valore del coefficiente di perdita superficiale. Le misure sono state eseguite alla frequenza fissa di 0.0121 Hz in atmosfera di azoto, a pressioni diverse comprese tra ∼10⁻² mTorr e 220 mTorr. L'estremità lontana del campione e le pareti del contenitore erano tenuti costantemente alla stessa temperatura (0°C), mentre il gradiente termico era sistematicamente variato tra 2°C e 12°C, in corrispondenza di ciascuna pressione. Operando in questo modo, si potevano variare opportunamente sia la conduzione sia l'irraggiamento del calore dalla superficie laterale del campione nel mezzo circostante. In queste misure, la causa predominante di errore viene dalla misura dello sfasamento delle due onde, che introduce nella valutazione diD un'incertezza del 2%. I valori sperimentali ottenuti nelle diverse condizioni prima ricordate risultano, in ogni caso, compresi entro i limiti di questa incertezza, poichéD=(1.17±0.02) cm²/s, in ottimo accordo con i dati della letteratura. Questo risultato dimostra pertanto che la diffusività termica, determinata con questo metodo dinamico, risulta effettivamente indipendente dalla quantità di calore transmesso dal campione nel mezzo circostante, consentendo pertanto piú agevoli determinazioni della conducibilità termica dei solidi, noti la densità ed il calore specifico.

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Резюме С помощью новой экспериментальной техники, основанной на нестационарном методе, т.е. на свойствах распространения тепловых волн, мы измеряем коэффициент температуропроводностиD медного провода, посредством измения граничных условий, чтобы выяснить независимость величинD от поверхностных потерь тепла. Температурные осцилляции при фиксированной частоте 0.0121 Гц возбуждаются на одном конце образца, который помеЩен в атмосферу азота при различных давлениях в области от ∼10⁻² мтор до 220 мтор. Температуры другого конца образца и стенок контейнера являются постояннюми 0°C, тогда как градиент температуры между средним значением осциллирующей темпертурой и этой постоянной температурой изменяется от 2°C до 12°C для каждого значения давления, за счет регулировки мощности нагревателя. Этот метод позволяет изменять тепловые потери, обусловленные либо проводимостью и конвекцией, либо излучением. Основная причина ошибок проистекает из неопределенности в измерениях фазового сдвига между тепловыми осцилляциями, заререгистрированными в двух фиксированных точках образца. Ошибка при измерении составляет около 2%. Экспериментальные значения, полученные для коэффициента температуропроводности при различных граничных условиях,D=(1.17±0.02) см⁻²с⁻¹, хорошо согласуются с данными в литературе. Полученные результаты показывают, что предложенный экспериментальный метод обладает большим преимуществом при определении температуропроводности и, следовательно, теплопроводности твердых тел, не уделяя особого внимания изоляции образца.

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To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.

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This research was supported by the Consiglio Nazionale delle Ricerche, Rome (Italy).

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Some preliminary results were presented at the ?LXVII Congresso della Società Italiana di Fisica?, Pisa, October 1981.     

Weather radar calibration by means of the metallic sphere and multiparameter radar measurements

Summary Absolute calibration is an important task in order to obtain reliable and accurate measurements of radar observables and derived meteorological parameters. In this paper two procedures are described; the first one is based on measuring the power received from a metallic sphere and the second utilizes the rainfall estimates obtained by the multiparameter radar measurements. The accuracy of the latter method is studied in detail from the simulation of the dual polarization measurables. The theoretical results are compared with radar measurements relative to a rain event.     

Surface state spectroscopy on zinc oxide crystals by means of modulated photoconductivity measurements

The spectral distribution of photoconductivity for photon energies between 0.2 and 2.5 eV was measured on ZnO crystals at low temperatures in ultrahigh vacuum (UHV). The prism surfaces (∥c axis) were cleaned by heating whereas the polar surfaces (⊥c axis) were prepared by cleavage in UHV. The spectra obtained on the three types of ZnO surfaces are different. Exposure to oxygen and to atomic hydrogen influences the absolute amount of photoconductivity. Therefore, an excitation from surface states is concluded and transition energies are derived.     

Stability measurements of a tunable single frequency He-Ne laser by means of self-locking phenomena

In two previous papers [8, 9] a theory has been developed for the phenomenon of selflocking in a pressure broadened three mode He-Ne laser. Using this phenomenon, a new method of measuring the frequency stability of another laser is presented. Actual measurements of the frequency stability of a 633 nm single frequency He-Ne laser by means of this new method are reported. The design and construction of the single frequency laser is described briefly. Using an intracavity quartz etalon, multimode to single mode output power conversion efficiencies as high as 92% have been observed in the range of several mW. Continuous tuning over a frequency range of 1.2 GHz is achieved by a combination of etalon tilting and resonator length variation. A frequency stability better than 110⁸ over periods of several min has been realized.     

Diffusion of gold in silicon studied by means of neutron-activation analysis and spreading-resistance measurements

In- and out-diffusion of gold in silicon were investigated with the aid of a neutronactivation analysis in combination with mechanical sectioning or by the spreadingresistance technique. In-diffusion profiles in the range 1371–1073 K show that Au diffuses in Si mainly via the so-called kick-out mechanism. From the Au diffusion and solubility measurements the interstitialcy contributionD _I ^SD to the Si self-diffusion coefficient was determined, which shows that the self-diffusion occurs to a considerable extent via selfinterstitials. Out-diffusion profiles at 1173 K were measured on wafers homogeneously supersaturated with Au. The observed decrease of the electrical activity of Au in the bulk indicates that during the out-diffusion anneal the majority of Au atoms originally dissolved substitutionally changes its configuration.     

Frequency measurements of far infrared laser lines by means of MIM point contact diodes

We present frequency measurements of 85 Far Infrared (FIR) laser lines ranging from 2 748 GHz to 421 GHz. We use the heterodyne technique of mixing FIR laser transitions and microwave radiation on MIM point contact diodes to determine the FIR frequencies.Work supported by Consiglio Nazionale delle Ricerche -Italia and INFM (Consorzio Interuniversitario di Fisica della Materia)     

Study of blue colour in ancient mosaic tesserae by means of thermoluminescence and reflectance measurements

The colouring effects of cobalt and copper ions in glass have been investigated by means of thermoluminescence and reflectance measurements. The two techniques have been used to characterise the colour centres of ancient blue glass mosaic tesserae, in comparison with standard modern colourless and blue glass. Thermoluminescence measurements allowed us to characterise the colour centres in the glass network and to evaluate the electron trap depth in ancient and modern samples. In ancient samples there is evidence of three electron traps, at the same temperatures of crystalline quartz, perhaps due to a partial re-crystallisation of the lattice. On the contrary, in modern samples, the continuum of trapping levels typical of amorphous silica is evident. PACS 78.66.Jg; 78.60.Kn; 78.40.Pg     

Determination of average domain size on permalloy and perminvar by means of complex permeability measurements

Our experiments were performed on industrial purity materials of 0.10–0.35 mm strip thickness. We tried to apply both the Polivanov bowing wall and the Pry-Bean rigid wall model for characterizing the domain structure of the materials. We proved experimentally that the main features of domain structure are in agreement with the assumptions of the bowing wall model. By means of fitting theoretical spectra on measured complex permeability spectra we determined the average size of domains as a function of thickness and annealing temperature. The number of domains related to one grain could be associated with changes of initial permeability and coercive force.