Electron transport through interacting quantum dots

We present a detailed theoretical investigation of the effect of Coulomb interactions on electron transport through quantum dots and double barrier structures connected to a voltage source via an arbitrary linear impedance. Combining real time path integral techniques with the scattering matrix approach we derive the effective action and evaluate the current-voltage characteristics of quantum dots at sufficiently large conductances. Our analysis reveals a reach variety of different regimes which we specify in details for the case of chaotic quantum dots. At sufficiently low energies the interaction correction to the current depends logarithmically on temperature and voltage. We identify two different logarithmic regimes with the crossover between them occurring at energies of order of the inverse dwell time of electrons in the dot. We also analyze the frequency-dependent shot noise in chaotic quantum dots and elucidate its direct relation to interaction effects in mesoscopic electron transport.Comment: 21 pages, 4 figures. References added, discussion slightly extende

СРАВНИТЕЛЬНАЯ ОЦЕНКА РЕЗУЛЬТАТОВ ОПЕРАТИВНОГО ЛЕЧЕНИЯ ПАЦИЕНТОВ С ИМПРЕССИОННЫМИ ПЕРЕЛОМАМИ ПЯТОЧНОЙ КОСТИ

Current prospective investigation with historical control was performed to compare functional results of less invasive surgical treatment of calcaneal comminuted fractures with ordinary surgical methods. Data of 40 patients is being analyzed. One patient was lost for follow up. Patients have been divided to four subgroups according to used surgical technologies. Groups differ by trauma on reposition and method of fracture’s fixation: open reduction and plating (ORIF), cannulated screws with triple thread (FusiFix), external fixation, other (diafixation, ordinary cortical or metaphyseal screws). Foot function was estimated by FAOS scale between 1 and six and more years after surgery. Combination of modified principles of reposition after Essex - Lopresti, using of original instrument set and C-arc with FusiFix stable fixation enables minimal complications add ratio. This method also creates good possibilities for foot functional recovery (average normalized FAOS index is 92 after 1 year comparatively to 60 (ORIF) and 57(ExFix)).Проспективное исследование с историческим контролем проведено с целью сравнения функциональных результатов малоинвазивных репозиции и остеосинтеза импрессионных переломов пяточной кости с иными методами, сочетающими открытую репозицию и фиксацию отломков. Материал и методы. В исследование включены 40 пациентов, один из которых впоследствии отказался от сотрудничества. В четырёх сравниваемых группах сочетали открытую репозицию с фиксацией костных отломков. Группы отличались степенью травматичности репозиции и способами фиксации: специализированные пластины (ORIF), канюлированные винты с тройной резьбой (FusiFix), внешняя фиксация (ExFix) и прочие (фиксация отрезками спиц, кортикальными и/или метафизарными винтами). Функция оперированной стопы оценивалась по шкале FAOS в интервале от 1 года до 6 и более лет. Результаты. Применение модифицированных принципов репозиции Essex-Lopresti, оригинального вспомогательного инструментария и электронно-оптической визуализации со стабильной фиксацией винтами FusiFix создаёт минимальный относительный риск осложнений. Эта комбинация также обеспечивает быстрые темпы функционального восстановления оперированной стопы (средний нормализованный балл FAOS через 1 год равен 92 баллам против 60 (ORIF) и 57 ExFix)

Search for direct production of a2(1320) and f2(1270) mesons in e+e- annihilation

A search for direct production of C-even resonances a2(1320) and f2(1270) in e+e- annihilation was performed with SND detector at VEPP-2M e+e- collider. The upper limits of electronic widths of these mesons were obtained at 90% confidence level: Gamma(a2(1320) \to e+e-) < 0.56 eV, Gamma(f2(1270) \to e+e-) < 0.11 eV.Comment: 6 pages, 5 figures, 1 table. Submitted to Phys. Lett.

New experimental data for the decays ϕ→μ+μ−\phi\to\mu^+\mu^- and ϕ→π+π−\phi\to\pi^+\pi^- from SND detector

The processes $e^+e^-\to\mu^+\mu^-$ and $e^+e^-\to\pi^+\pi^-$ have been studied with SND detector at VEPP-2M $e^+e^-$ collider in the vicinity of $\phi(1020)$ resonance. The branching ratios $B(\phi\to\mu^+\mu^-)=(3.30\pm 0.45\pm 0.32)\times 10^{-4}$ and $B(\phi\to\pi^+\pi^-)=(0.71\pm 0.11\pm 0.09)\times 10^{-4}$ were obtained.Comment: 5 pages, 4 figures, talk given at 8th International Conference on Hadron Spectroscopy (HADRON 99), Beijing, China, 24-28 Aug 199

The process e+e−→π+π−π0e^+e^-\to\pi^+\pi^-\pi^0 in the energy range 2E_0=1.04 - 1.38 GeV

In the experiment with the SND detector at VEPP-2M e^+e^- collider the process $e^+e^-\to\pi^+\pi^-\pi^0$ was studied in the energy range 2E_0 from 1.04 to 1.38 GeV. A broad peak was observed with the visible mass $M_{vis}=1220\pm 20$ MeV and cross section in the maximum $\sigma_0\simeq 4$ nb. The peak can be interpreted as a $\omega$-like resonance $\omega (1200)$.Comment: 10 pages LATEX and 5 figure

Experimental Study of rho -> pi0 pi0 gamma and omega -> pi0 pi0 gamma Decays

The e+e- -> pi0 pi0 gamma process was studied in the SND experiment at VEPP-2M e+e- collider in the energy region 0.60-0.97 GeV. From the analysis of the energy dependence of measured cross section the branching ratios B(omega -> pi0 pi0 gamma)= (6.6 +1.4-0.8(stat) +-0.6(syst))x10^-5 and B(rho -> pi0 pi0 gamma)=(4.1 +1.0-0.9(stat) +-0.3(syst))x10^-5 were obtained.Comment: 16 pages, 7 figures, submitted to Phys. Lett.

Nonstationary generation of electromagnetic radiation in nonequilibrium mirror-confined plasma

We demonstrate the use of a laboratory setup based on a magnetic mirror trap with plasma sustained by a gyrotron radiation under the electron cyclotron resonance conditions aimed at identifying the role of the background plasma as a trigger of the electron cyclotron instability. New regime of instability has been revealed during the plasma decay after the gyrotron switch-off when the plasma density becomes low enough, so that the electron plasma frequency is much less than the electron gyrofrequency. At this stage, we observe the excitation of electromagnetic waves which propagate nearly perpendicular to the magnetic field and cause precipitation of energetic electrons to the trap ends. The instability is detected as series of quasi-periodic broadband pulses of electromagnetic radiation (25…27 GHz frequency, typical pulse duration of 1…10 microseconds) and related precipitation of energetic (>10 keV) electrons. These emissions of the fast electrons can be attributed to the development of the kinetic instability of the extraordinary wave propagating quasiperpendicular to the magnetic field near the fundamental cyclotron harmonic.Исследованы временные и частотные характеристики квазипериодических импульсов электромагнитного излучения в распадающейся плазме импульсного ЭЦР-разряда в прямой аксиально-симметричной магнитной ловушке. Зарегистрированы серии квазипериодических импульсов электромагнитного излучения на частоте 25...27 ГГц с типичной длительностью импульса 1...10 мкс и связанные с ними высыпания энергичных (> 10 кэВ) электронов. Наблюдаемое излучение интерпретировано как результат резонансного взаимодействия горячих электронов с быстрой необыкновенной волной, распространяющейся в разреженной плазме поперек внешнего магнитного поля.Досліджено часові та частотні характеристики квазіперіодичних імпульсів електромагнітного випромінювання в плазмі, що розпадається, імпульсного ЕЦР-розряду в прямій аксіально-симетричній магнітній пастці. Зареєстровані серії квазіперіодичних імпульсів електромагнітного випромінювання на частоті 25...27 ГГц з типовою тривалістю імпульсу 1...10 мкс та пов'язані з ними висипання енергійних (> 10 кеВ) електронів. Випромінювання, що спостерігається, інтерпретовано як результат резонансної взаємодії гарячих електронів з швидкою незвичайною хвилею, що розповсюджується в розрідженій плазмі поперек зовнішнього магнітного поля

Radiative decays of light vector mesons

The new data on $\rho,\omega,\phi$ radiative decays into $\pi^0\gamma,\eta\gamma,\eta'\gamma$ from SND experiment at VEPP-2M $e^+e^-$ collider are presented.Comment: 5 pages, 2 figures, talk given at 8th International Conference on Hadron Spectroscopy (HADRON 99), Beijing, China, 24-28 Aug 199

Progress report of investigations on gyrotron ECR ion source SMIS 37

A review of experimental investigations on ion production in plasma developed on SMIS 37 source at the Institute of Applied Physics of RAS (Nizhny Novgorod) is reported. Pulsed power gyrotron with emission frequency 37.5 GHz was used for plasma creation and heating in the simple magnetic mirror trap. Magnetic field with value up to 3.5 T was created by pulsed coils. Experiments were carried out in nitrogen as operating gas. Formation of multicharged ions in dense plasma in different regimes of plasma confinement was investigated. In this report we describe some investigations of instabilities of the plasma in the trap. Low frequency instabilities are analyzed basing on the results of plasma high-speed image registration. Also, whistler cyclotron instability was observed. Short pulses of accelerated electrons with energy about 10 keV are measured. Detected short pulses of microwave emission of the plasma characterize cyclotron instability too. Dense plasma of singly charged ions obtained in the trap with the plug magnetic field much less than resonant value. Flux of the plasma exceeds 0,1 A/cm2, electron temperature is about 20 eV. Such plasma seems to be interesting for surface modification

Experimental study of the e+e- -> pi0 gamma process in the energy region sqrt(s)=0.60-0.97 GeV

Results of the study of the e+e-->pi0 gamma process with SND detector at VEPP-2M collider in the c.m.s. energy range sqrt(s)=0.60-0.97 GeV are presented. Using 36513 selected events corresponding to a total integrated luminosity of 3.4 pb^-1 the e+e-->pi0 gamma cross section was measured. The energy dependence of the cross section was analyzed in the framework of the vector meson dominance model. The data are well described by a sum of phi,omega,rho0->pi0 gamma decay contributions with measured decay probabilities: Br(omega->pi0 gamma)=(9.34+-0.15+-0.31)% and Br(rho0->pi0 gamma)=(5.15+-1.16+-0.73)*10^-4 . The rho-omega relative interference phase is phi(rho,omega}=(-10.2+-6.5+-2.5) degree