CO在Sm/Rh(100)模型表面上的吸附与反应

应用AES,LEED,XPS和TDS研究了Rh(100)上Sm膜和Sm/Rh表面合金以及CO在这两类模型表面的吸附与反应.室温下Sm在Rh(100)上的生长遵从SK模式,Sm膜经900K高温退火后可形成有序表面合金.在室温制备的Sm膜/Rh(100)表面上,室温下CO在Sm上的吸附改变了表面结构,生成SmOx和表面碳.随着Sm覆盖度的增加,低温脱附峰(α-CO)面积迅速下降,且峰温向高温方向位移;表明Sm的空间位阻和电子效应同时起作用.在Sm/Rh合金表面上,CO在约590K出现新的脱附峰,可归属为受Sm电正性修饰的Rh原子上的CO脱附峰     

Applications of Vibrational Spectroscopy for Analysis of Connective Tissues

Advances in vibrational spectroscopy have propelled new insights into the molecular composition and structure of biological tissues. In this review, we discuss common modalities and techniques of vibrational spectroscopy, and present key examples to illustrate how they have been applied to enrich the assessment of connective tissues. In particular, we focus on applications of Fourier transform infrared (FTIR), near infrared (NIR) and Raman spectroscopy to assess cartilage and bone properties. We present strengths and limitations of each approach and discuss how the combination of spectrometers with microscopes (hyperspectral imaging) and fiber optic probes have greatly advanced their biomedical applications. We show how these modalities may be used to evaluate virtually any type of sample (ex vivo, in situ or in vivo) and how “spectral fingerprints” can be interpreted to quantify outcomes related to tissue composition and quality. We highlight the unparalleled advantage of vibrational spectroscopy as a label-free and often nondestructive approach to assess properties of the extracellular matrix (ECM) associated with normal, developing, aging, pathological and treated tissues. We believe this review will assist readers not only in better understanding applications of FTIR, NIR and Raman spectroscopy, but also in implementing these approaches for their own research projects.     

Banach空间中太阳集对无穷序列的最佳同时逼近

本文研究太阳集对一列无穷序列的最佳同时逼近问题，建立了特征及唯一性结果．     

Thermoresponsive Ionic Liquid/Water Mixtures: From Nanostructuring to Phase Separation

The thermodynamics, structures, and applications of thermoresponsive systems, consisting primarily of water solutions of organic salts, are reviewed. The focus is on organic salts of low melting temperatures, belonging to the ionic liquid (IL) family. The thermo-responsiveness is represented by a temperature driven transition between a homogeneous liquid state and a biphasic state, comprising an IL-rich phase and a solvent-rich phase, divided by a relatively sharp interface. Demixing occurs either with decreasing temperatures, developing from an upper critical solution temperature (UCST), or, less often, with increasing temperatures, arising from a lower critical solution temperature (LCST). In the former case, the enthalpy and entropy of mixing are both positive, and enthalpy prevails at low T. In the latter case, the enthalpy and entropy of mixing are both negative, and entropy drives the demixing with increasing T. Experiments and computer simulations highlight the contiguity of these phase separations with the nanoscale inhomogeneity (nanostructuring), displayed by several ILs and IL solutions. Current applications in extraction, separation, and catalysis are briefly reviewed. Moreover, future applications in forward osmosis desalination, low-enthalpy thermal storage, and water harvesting from the atmosphere are discussed in more detail.     

Fe离子注入ZnO生成超顺磁纳米颗粒

过渡族元素掺杂ZnO生成稀磁半导体, 成为近期国际材料科学研究的热点. 在本文中, 研究Fe离子注入ZnO单晶的结构和磁性变化, 目标是建立磁性和结构的对应关系, 澄清铁磁性的来源. 采用卢瑟福背散射/沟道技术 (RBS/Channelling)、同步辐射X射线衍射 (SR-XRD)和超导量子干涉仪 (SQUID), 研究注入温度和退火对样品的晶格损伤、结构及磁性的影响. 研究表明: 样品注入区损伤随注入温度升高而降低; 低温253 K注入样品中, SR-XRD未检测到新相, Fe离子分布于Zn位, ZnO (0002) 峰右侧肩峰可能属于Zn_1-xFe_xO, 5 K下测试样品不具有铁磁性; 623 K注入和823 K真空退火 (253 K注入) 样品中形成α和γ相金属Fe, 5 K下样品具有明显的剩磁和矫顽力, 零场冷却和场冷却 (ZFC/FC) 曲线和300 K下的磁滞回线显示纳米Fe颗粒具有超顺磁性. Fe离子注入ZnO的磁性源于第二相α-Fe和γ-Fe. 关键词： 离子注入 ZnO 同步辐射X射线衍射 超顺磁性     

Landau-Level Quantization of the Yellow Excitons in Cuprous Oxide

Lately, the yellow series of P-excitons in cuprous oxide could be resolved up to the principal quantum number n = 25. Adding a magnetic field, leads to additional confinement normal to the field. Thereby, the transition associated with the exciton n is transformed into the transition between the electron and hole Landau levels with quantum number n, once the associated magnetic length becomes smaller than the related exciton Bohr radius. The magnetic field of this transition scales roughly as n^–3. As a consequence of the extended exciton series, we are able to observe Landau level transitions with unprecedented high quantum numbers of more than 75.     

Effects of a vocally fatiguing task and systemic hydration on phonation threshold pressure

Phonation threshold pressure (PTP), effort for speaking, and vibratory closure pattern were assessed in 4 women with normal untrained voices after 2 hours of loud reading. PTP generally increased after this vocally fatiguing task at conversational pitch and 10%, 50%, and especially 80% of the pitch range. Increased systemic hydration by drinking water appeared to attenuate and/or delay the elevation of PTP for 3 subjects, at least at the highest pitch tested. Effort for speaking increased consistently throughout the loud reading task and subsequently decreased after 15 minutes of vocal silence. Upon videostroboscopic examination of the larynx, 3 subjects demonstrated spindle-shaped vibratory closure patterns on occasion after loud reading. The results provide preliminary support for increasing water consumption to reduce or delay some vocal-function changes after prolonged loud phonation in untrained speakers.     

Transport properties of LaCu2Si2 and CeCu2Si2 between 1.5K and 300K

We report measurements of the electrical resistivity, the thermal conductivityk and the thermoelectric powerS between 1.5K and 300K on the anomalous CeCu₂Si₂ compound and on LaCu₂Si₂ as reference compound. For LaCu₂Si₂ the temperature dependences of andS are in accord with those found in otherd band metals. For CeCu₂Si₂ the observed resistivity (220 µ cm at 200K) leads to a very short electronic mean free path which is of the order of the Ce-Ce spacing. Correspondingly,k is almost identical with the phonon contributionk _p . Below 20K, resistivity and thermoelectric power strongly suggest Fermi liquid behavior with a degeneracy temperature between 20K and 40K. Above 200K, both andS decrease proportionally to –ln(T/1 K).Work performed within the research program of the Sonderforschungsbereich 125 Aachen/Jülich/KölnPart of this work will be presented at the Int. Conf. on Rare Earths in the Metallic State, St. Pierre de Chartreuse, Sept. 1978     

A one dimensional microscopical model for the study of the coherence in the stopping power problem. Part 3

We consider the quantum mechanical problem of a particle being scattered inelastically by a chain ofN infinitely heavy, equidistantly spaced two-level atoms. In a previous paper (Süßmann, G., Szilas, P.: Z. Phys. B — Condensed Matter42, 253 (1981)) the time dependent problem of a Gaussian wave packet impinging on the target atoms has been studied and an explicit asymptotic expression for the reduced density matrix ρ _R of the particle has been given. We now introduce the coarse grained density matrix \(\bar \rho _R\) . The incoherenceI?1-Tr( \(\bar \rho _R^2\) ), i.e. the deviation of the state of the particle from a pure state, being small on certain conditions, we find a single particle wave function ψ with \(\psi (x',t)\psi ^* (x'',t) \approx \left\langle {x'\left| {\bar \rho _R (t)} \right|x''} \right\rangle\) and a nonlinear Hermitean HamiltonianH _ψ=p ²/2m+W _ψ such thati?ψ(x, t)=H _ψψ(x, t) describes the time evolution. Finally we also considerW _ψ within the framework of the phenomenological theory of nonlinear frictional operators.     

Ionization of hydrogen and deuterium atoms in thermal energy collisions with state-selected Ne(3s 3 P 2,3 P 0) metastable atoms

High resolution energy spectra of electrons and ions resulting from thermal energy collisions of hydrogen and deuterium atoms with state-selected metastable Ne(Ne(3s ³ P ₂,³ P ₀) atoms are reported. The electron spectra for Ne(³ P ₂)+H(D) are very broad: The high energy part due to formation of NeH⁺ (NeD⁺) bound states (associative ionization), amounts to about 30% of the ionizing events, whereas the dominant part of the spectrum including a prominent low-energy peak is due to Penning ionization out of a strongly-attractive entrance potential curve. Comparison of the spectra with quantum mechanical fit calculations yields fairly accurate information on this potential, in particular its well depthD _e [Ne(³ P ₂)?H,D]= 2.0(1) eV. The spectra for Ne(³ P ₀)+H, D are comparatively narrow with much lower cross sections than the one for the Ne(³ P ₂) state. The corresponding entrance channel is a weakly bound van der Waals molecule with a well depth below 0.1 eV. A perturbation calculation of the Ne(3s)+H(1s) potential energy curves at large distances explains the observed difference between the Ne(³ P ₂)+H(D) and Ne(³ P ₀)+H(D) systems. Symmetry arguments are given that the major contribution to the Ne(³ P ₂)+H(D) spectra is due to the² Σ potential.