We used microwave radiation to evaporatively cool a mixture of of 133Cs and 87Rb atoms in a magnetic trap. A mixture composed of an equal number (around 104) of Rb and Cs atoms in their doubly polarized states at ultracold temperatures was prepared. We also used microwaves to selectively evaporate atoms in different Zeeman states. 相似文献
Summary Metallic samples subjected to heating-cooling cycles undergo a permanent change in their length. The difference between the
initial length and the length at the end of the cycle (residual strain) depends on the maximum temperature attained during
the cycle. This dependence of residual strain on the maximum temperature of the cycle is similar for all of the examined metals
(polycrystalline copper, aluminium, iron, gold, lead and single-crystal copper). Upon further increasing this temperature,
the metal residual strain changes from positive to negative values. The temperature at which the maximum positive residual
strain occurs is characteristic for each metal. The value of the residual strain and the temperature at which it changes its
sign depend on the previous thermal history of the metal. 相似文献
Abstact: The kinetic energy spectrum and the polarization of the PSI neutron beam produced in the reaction 12C(p,n)X at 0° with 590 MeV polarized protons were investigated. A strong energy dependence of the neutron beam polarization is
observed which was not expected at the time the neutron beam was built.
Received: 3 April 1998 相似文献
The polarization asymmetries A0y and Ay0, and the spin correlation parameter Ayy have been measured at SIN at 515 and 578 MeV using a transversally polarized proton beam and target. The results are compared with various theoretical models. 相似文献
The main structure around m = 2.15 GeV first observed by the Argonne group in the spin-dependent total cross section ΔσL is confirmed in the energy range available at SIN. A simultaneous study of the scattered particles at small angles has been carried out with success and gave the spin-correlation parameter A00kk for the pp elastic scattering and for the reaction pp → π+d. The contribution of the 3-body reactions to this spin-dependent total cross section has been deduced and found to be lower than the contribution of the π+d reaction even at 583 MeV. 相似文献
Alkali metals adsorbed to surface films of the polymer poydimethylsiloxane (PDMS) have been shown to exhibit a unique photodesorption
behavior, characterized by a frequency threshold and high efficiency. In this work, the temperature dependence of the photodesorption
yields of Na and Na2 from PDMS surfaces were measured between room temperature and 183 K. Over most of the temperature range, the yields exhibited
an Arrhenius behavior characterized by thermal activation energies of 0.36 eV and 0.34 eV for Na and Na2, respectively. These values are suggestive of a surface diffusion as one of the elementary steps in the photodesorption mechanism.
Moreover, the similarity of the two values indicates that the same elementary step applies to the desorption of both Na and
Na2.
Received 23 April 1999 and Received in final form 15 July 1999 相似文献
The paper is devoted to studies of regularly and singularly perturbed Markov chains with damping component. In such models, a matrix of transition probabilities is regularised by adding a special damping matrix multiplied by a small damping (perturbation) parameter ε. We perform a detailed perturbation analysis for such Markov chains, particularly, give effective upper bounds for the rate of approximation for stationary distributions of unperturbed Markov chains by stationary distributions of perturbed Markov chains with regularised matrices of transition probabilities, asymptotic expansions for approximating stationary distributions with respect to damping parameter, explicit coupling type upper bounds for the rate of convergence in ergodic theorems for n-step transition probabilities, as well as ergodic theorems in triangular array mode.
The negative effects of smoke exposure of grapes in vineyards that are close to harvest are well documented. Volatile phenols in smoke from forest and grass fires can contaminate berries and, upon uptake, are readily converted into a range of glycosylated grape metabolites. These phenolic glycosides and corresponding volatile phenols are extracted into the must and carried through the winemaking process, leading to wines with overtly smoky aromas and flavours. As a result, smoke exposure of grapes can cause significant quality defects in wine, and may render grapes and wine unfit for sale, with substantial negative economic impacts. Until now, however, very little has been known about the impact on grape composition of smoke exposure very early in the season, when grapes are small, hard and green, as occurred with many fires in the 2019–20 Australian grapegrowing season. This research summarises the compositional consequences of cumulative bushfire smoke exposure of grapes and leaves, it establishes detailed profiles of volatile phenols and phenolic glycosides in samples from six commercial Chardonnay and Shiraz blocks throughout berry ripening and examines the observed effects in the context of vineyard location and timing of smoke exposure. In addition, we demonstrate the potential of some phenolic glycosides in leaves to serve as additional biomarkers for smoke exposure of vineyards. 相似文献