Exact treatment of spontaneous emission in helical and solenoidal magnetic field

Summary In this paper we discuss the spectral properties of the radiation emitted by electrons moving in helical undulators and solenoids. The analysis is exact, in the sense that the electron beam is not assumed to be ultrarelativistic but the far-field condition is still retained. We also discuss the low-energy corrections, the limits of validity of the usual approximations and the relevance of our results to gyrotron-type devices.     

Analytic treatment of the relativistic motion of charged particles in electric and magnetic field

Summary Using the Boris mover, or other standard methods, the error pile-up in the computation of the relativistic orbit of charged particles in electric and magnetic fields becomes quickly excessive, if one wants to keep reasonably limited the number of points employed to build the particle orbit. An analytical solution becomes, therefore, desirable and its construction is the subject of the present work.

---

Riassunto Unsando il metodo di Boris, oppure altri metodi standard, l'accumulazione degli errori nella determinazione numerica delle orbite relativistiche di particelle cariche in campi elettrici e magnetici diventa intollerabile, se il numero dei punti impiegati per costruire le orbite stesse è mantenuto basso. Una soluzione analitica diviene quindi utile, e questa costituisce l'argomento del presente lavoro.

---

Резюме В рамках стндартных методов погрешность при вычислении релятивистской орбиты заряженных частиц в электронном и магнитном полях становится чрезмерно большой, если для построения орбиты часицы используется ограниченное число точек. В связи с этим конструируется аналитическое решение.

     

Towards a wave theory of charged-beam propagation

Summary Using a recentquantum-mechanical treatment of charged-beam propagation in which the emittance plays the role of Planck's constant, we construct a wave theory of the beam transport along guiding systems. We show that the distribution of a beam passing through quadrupole lenses can be described in terms of Gaussian beams. We discuss the role of Twiss parameters within this context and derive anABCD law for charged beam transport.     

永磁扭摆磁铁的同步辐射特性和结构分析

简要分析了永磁扭摆磁铁所产生的同步辐射光的基本特性，并得出永磁扭摆磁铁所产生的同步辐射光的辐射功率角分布和总功率.介绍了永磁扭摆磁铁的基本结构，并对起主要承载力的C型框架和整体结构进行了有限元分析，从而得到磁铁结构在不同情况下的变形.应用理论公式对C型框架的变形位移量进行了验证，为永磁扭摆磁铁的结构设计和进一步改进提供了理论依据. 关键词： 扭摆磁铁 同步辐射 C型框架 有限元分析     

Inferences concerning anatomy and physiology of the human brain based on its magnetic field

Summary Research in the evoked magnetic field reported in the last two years is reviewed. The studies have shown that the magnetic technique may be used 1) to reveal complementary aspects of the current sources common to evoked potential, 2) to identify the organization of the cerebral cortex and subcortical areas of the brain and 3) to measure functional properties of the active neural areas whose locations are identified. Paper presented at the ?IV International Workshop on Biomagnetism?, held in Rome, September 14–16, 1982.     

Dynamical properties of the 2D wigner crystal in a strong magnetic field

Summary The dispersion relations and the shear modulus of the 2D Wigner crystal (WC) in the presence of a strong magnetic field are evaluated using a density functional method which includes the effect of electronic correlations. Comparison is made with previous theoretical results on the magnetophonons and the shear modulus. The effect of correlation on the stability of the crystal is discussed. In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching.     

Slow magnetic fields of the brain preceding movement and speech

Summary Magnetic fields of the brain were recorded preceding selfinitiated finger, foot, toe movements, stimulus-triggered finger and toe movements, and speech. Slow magnetic-field shifts were found with morphology similar to coincident electrical potentials, but with very different distributions. Inferences from the data about localization of cerebral generators were discussed. These studies were supported by grants from the B.C. Research Council and N.S.E.R.C. of Canada.     

Cerebral magnetic fields associated with voluntary limb movements in man

Summary Voluntary limb movements are preceded by MEG shifts beginning even as early as 1.2 s before the movement. These shifts reverse polarity above the cortical motor representation area of the limb concerned. Preliminary reports of this study have been presented (1,2).     

First magnetic measurements of action currents in isolated cardiac Purkinje fibers

Summary We present the first measurements of the magnetic field associated with the action potential in a bundle of isolated cardiac Purkinje fibers. Our findings demonstrate the feasibility of using magnetic techniques to measure the axial current in a bundle of spontaneously active cardiac cells. Paper presented at the ≪IV International Workshop on Biomagnetism≫, held in Rome, September 14–16, 1982.     

High-resolution recordings of the magnetic activity of the His-Bundle in man

Summary The activity of the His-Purkinje system (HPS) in man has been measured magnetically with a SQUID magnetometer in the Berlin magnetically shielded room (BMSR) by using in addition band pass filtering (band width 0.5 Hz to 300 Hz) and averaging. The BMSR reduces the background noise level to less than in the region of white noise. Within thePR interval a ramp pattern was observed, changing its slope when crossing the median line of the heart. In addition, definite signals were recorded approximately 40 ms before the onset of ventricular activation.

---

Riassunto L'attività del sistema di His-Purkinje è stata misurata magneticamente usando un magnetometro SQUID nella camera schermata magneticamente di Berlino (BMSR) e usando in aggiunta filtraggio (banda passante da 0.5 Hz a 300 Hz) e tecniche di mediazione. La camera riduce il livello di rumore di fondo a meno di 4 nella regione a spettro bianco. All'interno dell'intervalloPR è stata osservata una struttura a rampa, la cui pendenza cambia segno attraversando la linea mediana del cuore. In aggiunta, sono stati registrati segnali ben definiti approssimativemente 40 ms prima dell'inizio dell'attivazione ventricolare.

---

Резюме йзмеряется активность НР системы у человека с помощью SQUID магнетометра в Берлинской магнитно экранированной комнате, используя фильтртрацию полосы пропускания (ширина полосы от 0.5 Гц до 300 Гц) и усреднение. Берлинская магнитно экранированная комната уменьшает уровень фонового шума до величины в области белого шума. ВнутриPR интервла наблюдается диаграмма с уклоном, причем величина ыклона меняется при пересечении медианной линии сердца. Кроме того, ориблизительно за 40 мс до наступления активности желудочка регистрируются определенные сигналы.

     

On the observation of anomalous electron emission from a thin film under the influence of an outside electric field

Summary It is established that accelerated secondary electrons with very low energies emitted from a thin surface layer where M?ssbauer absorption and normal photoeffect are taking place show two distinctly separated energy lines. The maximum of the first line corresponds to the applied accelerating voltage while that of the second one corresponds to about 30% higher energy. The investigations are performed with a magnetic beta-spectrometer and with an electrostatic analyser. It is found that the intensity of the second, ?anomalous? line depends on the nature of the emitting layer. A number of experiments confirming the reality of the observed effects are reported. This authors of this paper have agreed to not receive the proofs for correction.     

Somatosensory evoked magnetic fields: Mappings and the influence of the stimulus repetition rate

Summary Somatosensory evoked magnetic fields were compared with corresponding electric scalp potentials in order to study their neural sources. Mappings of the magnetic responses showed activity at the primary and secondary somatosensory cortices. Additional sources besides these areas seem to be involved in the generation of the somatosensory vertex scalp potentials. Paper presented at the ?IV International Workshop on Biomagnetism?, held in Rome, September 14–16, 1982.     

Anyon interpolation between exact integer and fractional quantum hall states in an electric field

Summary The exact perturbed Laughlin wave function in the presence of a quadratic central electric potential is deduced by the so-called adiabatic heuristic. The corresponding exact expression for the fractional quantum Hall current density, including electric-field inhomogeneity effects, is evaluated and shown to be related by a simple scaling transformation to that for the integer case. This leads to conjecture that the effect of disorder in the fractional case can be derived in general from that in the integer case. The author of this paper has agreed to not receive the proofs for correction.     

新型多用磁场实验(演示)仪

介绍了新型多用磁场实验(演示)仪的原理特点和功能，并进行了实际测量，结果和理论符合很好，它是一种较好的电磁学实验仪器，具有较高的推广价值。     

Evidence of the exciton-plasma transition in the emission spectra of GaSe

Summary We present luminescence spectra of gallium selenide at 2 K in which a slow and continuous evolution from excitonic recombination to an electron-hole plasma emission is observed when the excitation intensity is increased. We find a small red-shift and a broadening of the direct exciton emission line which is followed by its disappearing. We explain these results with a model which takes into account the electron-hole correlation. Part of this work was carried out during a stage at the Institut de Physique Appliquée of the Ecole Polytechnique Fédérale de Lausanne (Switzerland).     

Nonlinear surface polaritons in 2D electron system in high magnetic field

The paper deals with the theoretical investigation of nonlinear surface polaritons (NSP) in isolated two-dimensional electron system (2DES) arranged at the interface between linear and nonlinear media and placed into the external quantizing magnetic field directed perpendicularly to 2DES. We consider that nonlinear medium dielectric permeability depends upon the tangential component of electric field only. It is shown that under the integer quantum Hall effect conditions all NSP characteristics are represented by the quantized values. It is found that the NSP spectrum contains two NSP modes - high-frequency and low-frequency ones. It is shown that the NSP can exist only in the case where the value of tangential component of electric field at the interface is less than a certain critical value. It is found that the resonant interaction between the NSP high-frequency mode and surface polariton mode occurs in the vicinity of the cyclotron resonance subharmonic. Received 23 September 2001 / Received in final form 31 January 2002 Published online 2 October 2002 RID="a" ID="a"e-mail: bludov@ire.kharkov.ua     

Structure and bonding parameters in ternary and multinary compounds

Summary A new approach to the study of the structural properties of semiconductors is presented. It is based on a semi-classical approximation which allows us to obtain the structural properties directly from the knowledge of the crystal pseudopotential. Since it leads to analytic expressions, this approach is well suited to elucidate the connections between the crystal structure and the bonding parameters. The relations with previous semi-empirical methods are discussed, with particular attention to the method of the average nuclear effective charge. The metallization trends in multinary compounds are analysed in detail and an interpretation is given in terms of a critical length for the covalent bond. Paper presented at the ≪V International Conference on Ternary and Multinary Compounds≫, held in Cagliari, September 14–16, 1982.     

Bulk properties of excitons in external electric field studied by coherent band dynamics

Summary Bulk properties of the exciton-polariton dispersion in the presence of a uniform electric field and for frequencies near the first excitonic resonance are studied within the framework of Stahl’s coherent band dynamics. A relative simple expression for the excitonic susceptibility (and thus for the dispersion relation) is derived and applied for calculating the field dependence of the transverse excitonic frequency. By an appropriate choice of a certain fitting parameter the calculated energy shift agrees satisfactorily with experimental values obtained recently by Schultheis and K?hler.

---

Riassunto Si studiano le proprietà di massa della dispersione eccitone-polaritone in presenza di un campo elettrico uniforme e per frequenze vicine alla prima risonanza eccitonica, nell’ambito della dinamica di banda coerente di Stahl. Si deduce una semplice espressione relativa per la suscettività eccitonica (e quindi per la relazione di dispersione) e la si applica nel calcolo della dipendenza della frequenza eccitonica trasversa dal campo. Con la scelta appropriata di un adatto parametro lo spostamento di energia calcolato è in accordo in modo soddisfacente con i valori sperimentali ottenuti recentemente da Schultheis e K?hler.

---

Резюме В рамках когерентной зонной динамики Стахля исследуются объемные свойства экситон-поляритонной дисперсии в присутствии однородного электрического поля и при частотах вблизи первого экситонного резонанса. Выводится относительно простое выражение для экситонной восприимчивости (и, следовательно, для дисперсионного соотношения). Полученное выражение используется для вычисления зависимости поперечной экситонной частоты от поля. При соответсвующем выборе подгоночного параметра вычисленный энергетический сдвиг удовлетворительно согласуется с экспериментальными величинами, недавно полученными Шультесом и Кёхлером.

     

Signal enhancement in a r.f. SQUID using stochastic resonance

Summary We describe an experiment on a simple superconducting loop with a Josephson junction subject to a time-sinusoidal magnetic flux embedded in a noise background. The response is shown to display thestochastic-resonance effect, wherein the output signal-to-noise-ratio passes through a maximum at a critical value of the noise strength. Escape times probability density functions are also obtained experimentally Paper presented at the International Workshop ?Fluctuations in Physics and Biology: Stochastic Resonance, Signal Processing and Related Phenomana?, Elba, 5–10 June 1994.     

空间微弱电磁场的测试、屏蔽及应用

分析了空间电磁干扰对电镜等电子仪器的影响;讨论了电磁屏蔽的设计和空间磁场测试原理;采用自行设计的线包和微弱电磁场测试技术,分析实测了多家实验室,证明该方法简便易行;对检测输电线路的老化和微弱漏电也具有实际意义．