A LEED determination of the structures of Ru(001) and of CO/Ru(001)−(√3 × √3)R30°

The structures of Ru(001) and of the √3 × √3 R30° overlayer of CO on Ru(001) have been determined by LEED I–V measurements and comparison to calculations. Special attention was paid to accurate angular alignment, selection of a well-ordered portion of the surface, and avoidance of beam-induced changes of the CO layer. Five orders of reflexes over a range of 300 eV each were used for the clean surface and 7 orders over 200 eV each for the CO superstructure. For the clean surface, a slight contraction of the first layer spacing (by 2%) was found which gave r-factors of 0.04 (Zanazzi-Jona) and 0.16 (Pendry) for 5 non-degenerate beams. For the CO structure the most probable geometry is the on-top site with spacings d(Ru---C) = 2.0 ± 0.1 Åandd(C---O) = 1.10 ± 0.1 Å (rZJ = 0.21; rP = 0.51). The two threefold hollow and the bridge sites can be clearly excluded

ESTIMATION OF CENTER OF MASS VELOCITY BY RIGHT POSTERIOR SPINE ILIAC LANDMARK DURING COUNTERMOVEMENT JUMP

When the impulse phase is proceeded by approach movement (e.g. volleyball spike jump), the vertical velocity of CoM at the beginning of the impulse phase must be known. To reduce the number of landmarks, the aim of this study was to verify the concordance between the velocity of CoM and the Right Posterior Spine Iliac at touchdown after flight phase. Ten female volleyball players of the first national volleyball league of Austria performed ten maximal CMJ without arm movement. Paired t-test was used to compare velocities between the two methods. No significant differences between the methods with maximal individual differences lower than 0.1m/s at touchdown could be found. If only the landing velocity at touchdown must be known, it seems to be sufficient to determine the velocity of Right Posterior Spine Iliac landmark

spike jump biomechanics in male versus female elite volleyball players

ABSTRACTThere are well-known biological differences between women and men, especially in technical-coordinative variations that contribute to sex differences in performance of complex movements lik..

Kaon and Antikaon Production in Heavy Ion Collisions at 1.5 AGeV

At the Kaon Spectrometer KaoS at SIS, GSI the production of kaons and antikaons in heavy ion reactions at a beam energy of 1.5 AGeV has been measured for the collision systems Ni+Ni and Au+Au. The K-/K+ ratio is found to be constant for both systems and as a function of impact parameter but the slopes of K+ and K- spectra differ for all impact parameters. Furthermore the respective polar angle distributions will be presented as a function of centrality.Comment: 4 pages, 4 figures, SQM2001 in Frankfurt, Sept.2001, submitted to Journal of Physics

Associação entre tempo de reação e de movimento em jogadores de futsal

The aim of the study was to verify the level of association between simple reaction time (RT) and movement time (MT) of young indoor soccer (futsal) players (13.8 ± 0.5 years, n = 16). Simple RT was measured using the Multipsy 821 apparatus with a button pressing movement as an answer to a light stimulus. MT, turning the body to the left or right, was measured by a system composed of a contact carpet, fixed on the ground, and two pairs of doubled-photocells. The beginning of the movement was registered by loss of contact with the contact carpet and the end of the movement was recorded when the player passed through the pair of doubled-photocells. The distance between the contact carpet and the first pair of photocells was 1.45 m. Statistical analysis did not indicate significant correlation for both variables. The results can be explained by differences in the structure of the used tests and by RT and MT measurement in different motor skills. Moreover, these movements have distinct demands related to body mass. To conclude, TR performance cannot be associated with the potentiality of an athlete to perform rapid body rotation movements.O objetivo do presente estudo foi verificar a associação entre tempo de reação (TR) simples e o tempo de movimento (TM) em jogadores de futsal jovens (13,8 ± 0,5 anos, n = 16). O TR simples foi medido no aparelho Multipsy 821, pressionando com o dedo indicador uma tecla em resposta a um sinal luminoso. O TM, giro do corpo para direita ou esquerda, foi mensurado por meio de um sistema composto por um tapete de contato, fixado ao solo, e dois pares de fotocélulas. O início e o final do movimento foram registrados pela perda de contato do pé do atleta com o tapete de contato e quando o atleta ultrapassava um par de fotocélulas duplas, respectivamente. A distância entre o tapete de contato e o primeiro par de fotocélulas foi de 1,45 m. A análise estatística não indicou correlação significativa entre as duas variáveis. Uma possível explicação para os resultados está relacionada com a estrutura dos testes utilizados e a mensuração do TR e TM em ações motoras distintas. Pode-se concluir, que o desempenho do TR simples não deve ser associado à potencialidade do atleta em realizar movimentos rápidos de giro

Impure Public Goods and Technological Interdependencies

Impure public goods represent an important group of goods. Almost every public good exerts not only effects which are public to all but also effects which are private to the producer of this good. What is often omitted in the analysis of impure public goods is the fact that – regularly – these private effects can also be generated independently of the public good. In our analysis we focus on the effects alternative technologies – independently generating the private effects of the public good – may have on the provision of impure public goods. After the investigation in an analytical impure public good model, we numerically simulate the effects of alternative technologies in a parameterized model for climate policy in Germany

Precautionary Effect and Variations of the Value of Information

For a sequential, two-period decision problem with uncertainty and under broad conditions (non-finite sample set, endogenous risk, active learning and stochastic dynamics), a general sufficient condition is provided to compare the optimal initial decisions with or without information arrival in the second period. More generally the condition enables the comparison of optimal decisions related to different information structures. It also ties together and clarifies many conditions for the so-called irreversibility effect that are scattered in the environmental economics literature. A numerical illustration with an integrated assessment model of climate-change economics is provided