Electron spin synchronization induced by optical nuclear magnetic resonance feedback

We predict a new physical mechanism explaining the electron spin precession frequency focusing effect observed recently in singly charged quantum dots exposed to a periodic train of resonant circularly polarized short optical pulses [A. Greilich et al, Science 317, 1896 (2007), Ref. 1]. We show that electron spin precession in an external magnetic field and a field of nuclei creates a Knight field oscillating at the frequency of nuclear spin resonance. This field drives the projection of the nuclear spin onto magnetic field to the value that makes the electron spin precession frequency a multiple of the train cyclic repetition frequency, which is the condition at which the Knight field vanishes.Comment: 4+ pages, 3 figure

Long-term Dynamics of the Electron-nuclear Spin System of a Semiconductor Quantum Dot

A quasi-classical theoretical description of polarization and relaxation of nuclear spins in a quantum dot with one resident electron is developed for arbitrary mechanisms of electron spin polarization. The dependence of the electron-nuclear spin dynamics on the correlation time $\tau_c$ of electron spin precession, with frequency $\Omega$, in the nuclear hyperfine field is analyzed. It is demonstrated that the highest nuclear polarization is achieved for a correlation time close to the period of electron spin precession in the nuclear field. For these and larger correlation times, the indirect hyperfine field, which acts on nuclear spins, also reaches a maximum. This maximum is of the order of the dipole-dipole magnetic field that nuclei create on each other. This value is non-zero even if the average electron polarization vanishes. It is shown that the transition from short correlation time to $\Omega\tau_c>1$ does not affect the general structure of the equation for nuclear spin temperature and nuclear polarization in the Knight field, but changes the values of parameters, which now become functions of $\Omega\tau_c$. For correlation times larger than the precession time of nuclei in the electron hyperfine field, it is found that three thermodynamic potentials ($\chi$, $\bm{\xi}$, $\varsigma$) characterize the polarized electron-nuclear spin system. The values of these potentials are calculated assuming a sharp transition from short to long correlation times, and the relaxation mechanisms of these potentials are discussed. The relaxation of the nuclear spin potential is simulated numerically showing that high nuclear polarization decreases relaxation rate.Comment: RevTeX 4, 12 pages, 9 figure

Влияние пищевого фактора на микроэволюцию колорадского жука

Many-sided research of interaction of Colorado beetle and fodder plant (potato, nightshade sweetly-bitter) defines the role of the plants as guiding factor of microevolutional processes in pest population.Різнобічні аспекти взаємодії колорадського жука з кормовою рослиною (картопля, паслін солодко-гіркий) визначили роль цих рослин як напрямного фактора мікроеволюційних процесів у популяції шкідника.Різнобічні аспекти взаємодії колорадського жука з кормовою рослиною (картопля, паслін солодко-гіркий) визначили роль цих рослин як напрямного фактора мікроеволюційних процесів у популяції шкідника

Effect of external magnetic field on electron spin dephasing induced by hyperfine interaction in quantum dots

We investigate the influence of an external magnetic field on spin phase relaxation of single electrons in semiconductor quantum dots induced by the hyperfine interaction. The basic decay mechanism is attributed to the dispersion of local effective nuclear fields over the ensemble of quantum dots. The characteristics of electron spin dephasing is analyzed by taking an average over the nuclear spin distribution. We find that the dephasing rate can be estimated as a spin precession frequency caused primarily by the mean value of the local nuclear magnetic field. Furthermore, it is shown that the hyperfine interaction does not fully depolarize electron spin. The loss of initial spin polarization during the dephasing process depends strongly on the external magnetic field, leading to the possibility of effective suppression of this mechanism.Comment: 10 pages, 2 figure

Electron loss of fast heavy projectiles in collision with neutral targets

The multiple electron loss of heavy projectiles in fast ion-atom collisions has been studied in the framework of the sudden perturbation approximation. Especially, a model is developed to calculate the cross sections for the loss of any number of electrons from the projectile ion, including the ionization of a single electron and up to the complete stripping of the projectile. For a given collision system, that is specified by the (type and charge state of the) projectile and target as well as the collision energy, in fact, the experimental cross sections for just three final states of the projectile are required by this model in order to predict the loss of any number, $N$, of electrons for the same collision system, or for any similar system that differs only in the energy or the initial charge state of the projectile ion. The model is simple and can be utilized for both, the projectile and target ionization, and without that large computer resources are requested. Detailed computation have been carried out for the multiple electron loss of Xe$^{18+}$ and U$^{6+,\, 10+,\, 28+}$ projectiles in collision with neutral Ar and Ne gas targets

Apolipoprotein A-I increases the activity of lysosomal glycosidases in the liver of mice with BCG-induced tuberculosis inflammation

This work shows the ability of apolipoprotein A-I to influence the activity of lysosomal glycosidases in the liver of mice in a model of BCG-induced tuberculous inflammation. The aim of the investigation was to study the activity of lysosomal glycosidases in the liver of mice using a model of BCG-induced tuberculous inflammation after intravenous administration of apolipoprotein A-I. Material and methods. The studies were performed on male CBA mice weighing 20-22 g. Disseminated tuberculous inflammation was modeled by a single intraperitoneal injection of 0.5 mg of BCG vaccine. The activity of lysosomal glycosidases was assessed spectrofluorimetrically by the content of hydrolysis products of the corresponding fluorogenic substrates. Results. Tuberculous inflammation led to a pronounced decrease in the activity of lysosomal glycosidases in the liver. Thus, β-galactosidase was decreased 2.3 times, β-glucosidase – 2.8 times, β-glucuronidase – 2.5 times compared with healthy animals. Intravenous injection of apolipoprotein A-I to animals against the background of BCG infection prevented a significant decrease in the enzymatic activity of glycosidases and these values practically did not differ from the control values. Conclusions. Enzymatic activity of lysosomal glycosidases in the group of mice with intravenous administration of apolipoprotein A-I against the background of BCG infection was 1.5–2 times higher than the corresponding indicators in the group of animals with BCG-infection without administration of apolipoprotein A-I, i.e. without treatment

The comparative analysis of numerous sketch in generalized mathematical programming with traditional methods of optimization at automated management flow distribion in SWFD

При розробцi автоматизованої системи управлiння потокорозподiлом в СПРВ на довгому iнтервалi часу важну роль вiдiграє побудування моделi об’єкту, яка адекватно вiдображає технологiчнi процеси, якi мають мiсце в системах подачi й розподiлу води. Показано, що моделi, якi використовувались ранiше, є наближенними, що зводять багатокритерiальну задачу пiдтримки прийняття рiшень до скалярної задачi випуклого математичного програмування. В статтi пропонується математично формулювати задачу як задачу узагальненого математичного програмування, й використовувати для її вирiшення багатокрокову схему узагальненого математичного програмування. Показано, що алгоритм, який реалiзує вирiшення сформульованої задачi, може мати рiзну iнформацiйну структуру, пропонується використовувати послiдовний вибiр, який реалiзується послiдовною схемою узагальненого математичного програмування (ПсОМП). В статтi наведено порiвняльний аналiз запропонованого алгоритму з найбiль вiдомим з iснуючих—диференцiальним алгоритмом проф. Євдокимова А.Г., який реалiзує вирiшення задачi структурно-параметричної оптимiзацiї СПРВ. Аналiз довiв перевагу розробленого алгоритму над iснуючим по всiм критерiям. Алгоритм був реалiзований у виглядi пакету прикладних програм, який впроваджений в виробництво пiдприємств управлiння водопровiдно-каналiзацiйних господарств Донецького регiону України.In creation of automated system that controls a f low distribution in SWFD on a long interval of time the important role is played by the object model’s construction that describes technological processes proceeding in SWFD adequately. It is shown, that the models used before are approximate. They have reduced supporting acceptance of the decision’s task to the task of convex mathematical programming. In the given article there is offered to formulate a task mathematically, as task of the generalized mathematical programming, and to use for its decision the multistep sketch of generalized mathematical programming. There is the algorithm’s realizing the decision of formulated task. The algorithm can have various information structures, and it is offered to use a consecutive choose, which is realized by consecutive sketch of the generalized mathematical programming "CsGMP". There is given the comparative analysis in the article with differential algorithm of the professor Evdokimov. Is realizes the decision of a structural-parametrical optimization’s task of SWFD. The analysis has proved the advantage of the developed algorithm above existing. The algorithm is realized as the software package, which is introduced into industry IEWSE of Donetsk region in Ukraine. (Industrial enterprise ofwater-sewerage economy