822 research outputs found
Wave packet dynamics in a monolayer graphene
The dynamics of charge particles described by Gaussian wave packet in
monolayer graphene is studied analytically and numerically. We demonstrate that
the shape of wave packet at arbitrary time depends on correlation between the
initial electron amplitudes and on the
sublattices and correspondingly (i.e. pseudospin polarization). For the
transverse pseudospin polarization the motion of the center of wave packet
occurs in the direction perpendicular to the average momentum . Moreover, in this case the initial wave packet splits
into two parts moving with opposite velocities along . If the
initial direction of pseudospin coincides with average momentum the splitting
is absent and the center of wave packet is displaced at along the same
direction. The results of our calculations show that all types of motion
experience {\it zitterbewegung}. Besides, depending on initial polarization the
velocity of the packet center may have the constant component ,
where is the Fermi velocity and is a function of
the parameter ( is the initial width of wave packet). As a result,
the direction of the packet motion is determined not only by the orientation of
the average momentum, but mainly by the phase difference between the up- and
low- components of the wave functions. Similar peculiarities of the dynamics of
2D electron wave packet connected with initial spin polarization should take
place in the semiconductor quantum well under the influence of the Rashba
spin-orbit coupling.Comment: 7 pages, 8 figures, to be published in Phys. Rev.
Функції держави у регулюванні відносин власності
ДВНЗ «Київ. нац. екон. ун-т ім. Вадима Гетьмана»Окреслено основні функції держави в регулюванні трансформаційними процесами в системі і відносинах власності на нинішньому етапі розвитку ринкової економіки в Україні. Обґрунтовано, що вдосконалення відносин власності має здійснюватися шляхом формування раціональної структури власності та бюджетних видатків, якісного правового поля, ефективної системи контролю, якісної нормативно-правової бази, підвищення конкурентоспроможності національного виробництва.Определены основные функции государства в регулировании трансформационными процессами в системе и отношениях собственности на нынешнем этапе развития рыночной экономики в Украине. Обосновано, что совершенствование отношений собственности должно осуществляться путем формирования рациональной структуры собственности и бюджетных расходов, качественного правового поля, эффективной системы контроля, качественной нормативно-правовой базы, повышения конкурентоспособности национального производства.The basic functions of the state in regulating the transformation processes in the system and property relations at the present stage of development of the market economy in Ukraine are determined in the article. It is proved that the improvement of relations of ownership must be achieved by the formation of a rational structure of ownership and low cost, high quality legal framework, an effective control system, high-quality regulatory framework, improve the competitiveness of domestic production
Wave packet dynamics in hole Luttinger systems
For hole systems with an effective spin 3/2 we analyzed analytically and
numerically the evolution of wave packets with the different initial
polarizations. The dynamics of such systems is determined by the
Luttinger Hamiltonian. We work in the space of arbitrary superposition of
light- and heavy-hole states of the "one-particle system". For 2D packets we
obtained the analytical solution for the components of wave function and
analyzed the space-time dependence of probability densities as well as angular
momentum densities. Depending on the value of the parameter ( is
the average momentum vector and is the packet width) two scenarios of
evolution are realized. For the initial wave packet splits into two
parts and the coordinates of packet center experience the transient
oscillations or {\it Zitterbewegung} (ZB) as for other two-band systems. In the
case when remains
almost cylindrically symmetric and the ripples arise at the circumference of
wave packet. The ZB in this case is absent. We evaluated and visualized for
different values of parameter the space-time dependence of angular momentum
densities, which have the multipole structure. It was shown that the average
momentum components can precess in the absence of external or effective
magnetic fields due to the interference of the light- and heavy hole states.
For localized initial states this precession has a transient character.Comment: 9 pages, 8 gigur
Опыт применения нетрадиционных удобрений при выращивании сеянцев сосны обыкновенной (Рinus sylvestris l.) на Урале)
Представлена информация о возможности использования нетрадиционных удобрений, которые приготовлены на основе отходов производств. В настоящее время они являются доступными, недорогими и высокоэффективными средствами повышения плодородия лесных почв. Проанализированы изменения параметров посадочного материала при внесении данных смесе
Space-time evolution of Dirac wave packets
In this work we study the dynamics of free 3D relativistic Gaussian wave
packets with different spin polarization. We analyze the connection between the
symmetry of initial state and the dynamical characteristics of moving particle.
The corresponding solutions of Dirac equation having different types of
symmetry were evaluated analytically and numerically and after that the
electron probability densities, as well as, the spin densities were visualized.
The average values of velocity of the packet center and the average spin were
calculated analytically, and the parameters of transient Zitterbewegung in
different directions were obtained. These results can be useful for the
interpretation of future experiments with trapped ions.Comment: 10 pages, 7 figure
Adenine and guanine recognition of stop codon is mediated by different N domain conformations of translation termination factor eRF1
Positioning of release factor eRF1 toward adenines and the ribose-phosphate backbone of the UAAA stop signal in the ribosomal decoding site was studied using messenger RNA (mRNA) analogs containing stop signal UAA/UAAA and a photoactivatable cross-linker at definite locations. The human eRF1 peptides cross-linked to these analogs were identified. Cross-linkers on the adenines at the 2nd, 3rd or 4th position modified eRF1 near the conserved YxCxxxF loop (positions 125–131 in the N domain), but cross-linker at the 4th position mainly modified the tripeptide 26-AAR-28. This tripeptide cross-linked also with derivatized 3′-phosphate of UAA, while the same cross-linker at the 3′-phosphate of UAAA modified both the 26–28 and 67–73 fragments. A comparison of the results with those obtained earlier with mRNA analogs bearing a similar cross-linker at the guanines indicates that positioning of eRF1 toward adenines and guanines of stop signals in the 80S termination complex is different. Molecular modeling of eRF1 in the 80S termination complex showed that eRF1 fragments neighboring guanines and adenines of stop signals are compatible with different N domain conformations of eRF1. These conformations vary by positioning of stop signal purines toward the universally conserved dipeptide 31-GT-32, which neighbors guanines but is oriented more distantly from adenines
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