8He Spectroscopy in Stopped Pion Absorption By 9Be

Level structure of 8He has been studied in the reaction of stopped pion absorption by 9Be nuclei. The missing mass spectrum in the range 0 MeV ≤ MM ≤ 10 MeV has been described by the superposition of phase-space distributions and the three states of 8He. Parameters of these states have been compared with data of other experimental and theoretical works

Vertical transport and electroluminescence in InAs/GaSb/InAs structures: GaSb thickness and hydrostatic pressure studies

We have measured the current-voltage (I-V) of type II InAs/GaSb/InAs double heterojunctions (DHETs) with 'GaAs like' interface bonding and GaSb thickness between 0-1200 \AA. A negative differential resistance (NDR) is observed for all DHETs with GaSb thickness $>$ 60 \AA below which a dramatic change in the shape of the I-V and a marked hysteresis is observed. The temperature dependence of the I-V is found to be very strong below this critical GaSb thickness. The I-V characteristics of selected DHETs are also presented under hydrostatic pressures up to 11 kbar. Finally, a mid infra-red electroluminescence is observed at 1 bar with a threshold at the NDR valley bias. The band profile calculations presented in the analysis are markedly different to those given in the literature, and arise due to the positive charge that it is argued will build up in the GaSb layer under bias. We conclude that the dominant conduction mechanism in DHETs is most likely to arise out of an inelastic electron-heavy-hole interaction similar to that observed in single heterojunctions (SHETs) with 'GaAs like' interface bonding, and not out of resonant electron-light-hole tunnelling as proposed by Yu et al. A Zener tunnelling mechanism is shown to contribute to the background current beyond NDR.Comment: 8 pages 12 fig

THE CHOICE OF FORMS OF COOPERATION WITH THE USE OF A MATRIX “THE LANDSCAPE OF ENTERPRISE”

The article gives the solution of the urgent tasks of increasing the efficiency and competitiveness of the enterprise in the conditions of the intra-industry division of labour. To solve this problem the author’s method of choice of forms of cooperation. The proposed method consists in the use of multidimensional matrix “landscape of the enterprise”. In the “landscape of the enterprise” is used five groups of indicators process: indicators input indicators output indicators control indicators required in the process of resources, indicators of functioning of the process. Each group of indicators consists of a set of indicators. As indicators management proposed to use copyrighted performance indicators management: integrated indicator of the cost of management, integrated indicator of management error, coefficient of the quality of regulation, the ratio of overhead costs, the coefficient of efficiency of regulation. For calculation of the quantitative control is proposed to use the control circuit developed by the company “Integrator of IT” together with the Department “Economics and organization of production” MSTU named N. Bauman

The results of research on the effectiveness of line management

The article proves the relevance of research concerning the management system effectiveness in the project company. It shows that the emergence of independent commercial enterprises in the electrical power sector led both to deterioration of continuous processes controllability and to serious failures in functioning of infrastructure processes (repairs, invoice, and receipt of monetary funds). But, at the same time, a number of processes showed an increase of operation efficiency due to decrease in expenses when functioning.Coordination of activities between holding and company showed that process to come up with the weighty arguments in favor of one or other management decisions was the most complicated.The objective of the article is worded as follows: to reveal the regularities for the management efficiency to depend both on the echelons of regulation to make a decision at various times of delay (time from the decision-making moment before impact on object/subject of management) and on the abovementioned factors.The research was carried out using the model of the control loop. When conducting research, the model used only line (proportional) link, as the most often encountered in the development of management systems in organizations. Line (proportional) link is the link with the output value changing with time according to the same law, as the input value. In management the proportional link means that managerial decisions and the impact on employees is proportional to the rejection of planned and actual performances of company activities.To assess the quality of management at different stages of the regulation, principles of regulation and management structures the article suggests to use the indicators of management costs, the integrated indicator of management error, the coefficient of regulation quality, the ratio of discounted costs, and the efficiency of regulation. It also proposes to use the efficiency factor of regulation to show which part of amended, as a result of regulation, external disturbance corresponds to one unit of costs for regulation.The dependences of the efficiency coefficient of regulation on the time delays in the process of decision-making at various regulatory principles are illustrated.The conclusions are based on results of research.</p

A self-consistent investigation of the semimetal-semiconductor transition in InAs/GaSb quantum wells under external electric fields

We investigate the phase transitions in InAs/GaSb quantum wells sandwiched between two wide-gap AlSb barrier layers under an external electric field perpendicular to interfaces. The Schrodinger and the Poisson equations are solved self-consistently to derive the subband dispersions, the potential profile, the electron charge distribution in the InAs layer, and the hole charge distribution in the GaSb layer. The Burt-Foreman envelope function theory and the scattering matrix method are used to solve the Schrodinger equation in the framework of the eight-band k (.) p model, including the spin-splitting of subbands in our calculation. We have found that in a thick InAs/GaSb quantum well, which has been investigated experimentally by Cooper et al (1998 Phys. Rev. B 57 11915), under low external electric fields, two electron levels stay below the highest hole level at zero in-plane wavevector k(parallel to) = 0. Then, the anticrossings of electron and hole levels produce several minigaps in the inplane dispersions, inside which the states of other subbands exist. As a result, the system is in a sernimetal phase. With increasing external electric field, the semimetal phase changes to semiconductor phase with only one hybridization gap. When all electron levels become higher than the hole levels at higher electric fields, the system has a semiconducting gap

Spin polarization of an electron-hole gas in InAs/GaSb quantum wells under a dc current

We have investigated the spin polarization of electrons and holes in InAs/GaSb broken-gap quantum wells under nonequilibrium conditions when a dc electric field is applied parallel to interfaces. The existence of a nonzero asymmetric part of the quasiparticle distribution function caused by the dc current and the spin-split of the electron-hole hybridized states generates a finite spin polarization in both the InAs layer and the GaSb layer. With a very weak asymmetry of the distribution function, our self-consistent calculation yields about 1% spin polarization for electrons in the InAs layer and holes in the GaSb layer. The signs of these spin polarizations depend on the widths of the layers, changing the widths drives a phase transition in the electron-hole gas between the hybridized semiconducting phase and the normal semiconducting phase. In the hybridized semiconducting phase, the spin polarizations in both the InAs layer and the GaSb layer have the same sign. Crossing the phase boundary, the electron spin polarization and the total spin polarization in the InAs/GaSb quantum well can change their signs

Cyclotron masses and g-factors of hybridized electron-hole states in InAs/GaSb quantum wells

Using the eight-band k center dot p model and the Burt-Foreman envelope function theory to perform self-consistent calculations, we have studied the effect of electron-hole hybridization on the cyclotron masses m(*) and the effective g-factors g(*) of two-dimensional quasiparticles in InAs/GaSb quantum wells under a magnetic field applied perpendicular to the interfaces. We can modify the degree of hybridization by changing the InAs and/or GaSb layer width, or by inserting a thin AlSb barrier. While electron-light-hole hybridization dominates at both low and high fields, due to a sequence of anticrossings between electronlike and heavy-holelike levels, there is also an important contribution from heavy-hole states to the strong hybridization in the intermediate field range. The field-dependence of the hybridized energy eigenstates is manifested in the variations of m(*) and g(*). Characteristic discontinuous changes of both m(*) and g(*) appear at each anticrossing, resulting in a magnetic-field-driven oscillating behavior of these quantities for electronlike states of a given Landau level index. The electron g-factor can change sign when two eigenstates anticross. Hybridization of electron and hole states enhances the electron effective mass, and we have found a complicated dependence of this effect on the interaction strength. Without inserting an AlSb barrier, the strong interaction between the electronlike and the light-holelike states at low magnetic fields produces a large level repulsion, and hence relatively small effective masses and g-factors associated with these states. Intermediate interaction leads to weaker level repulsion and therefore very heavy electron cyclotron masses as well as large g-factors associated with the lowest Landau levels. A weak interaction only enhances the cyclotron masses of the electronlike states slightly. The hole effective masses change with both the magnetic field and the sample structure in a more complicated fashion

Formation of 8^{8}He in the 9^{9}Be(π–^{–}, p)X and 10^{10}B(π–^{–}, pp)X Stopped Pion Absorption Reactions

The structure of levels of the $^{8}$He heavy helium isotope has been studied in the $^{9}$Be$({{\pi }^{ - }},p)X$ and $^{10}$B$({{\pi }^{ - }},pp)X$ stopped pion absorption reactions. Measurements have been performed with a two-arm multilayer semiconductor spectrometer at the LANL. Indications to the existence of a soft dipole mode at the excitation energy ${{E}_{x}} \approx 3$ MeV have been obtained. A state with a high excitation energy of 12.2(5) MeV has been observed for the first time