早期腰池置管引流治疗伴有恶性颅高压的新型隐球菌脑膜炎

为观察早期腰池置管引流治疗伴有恶性颅高压的新型隐球菌脑膜炎患者的临床效果,对7例伴有恶性颅高压的新型隐球菌脑膜炎患者采用早期腰池置管引流（最长引流4周）,同时给予两性霉素-B静脉、鞘内注射及5-氟胞嘧啶口服等常规治疗,以隐球菌计数、墨汁染色阴性时间及临床症状改善情况为观察指标。结果表明,有头痛、呕吐、意识障碍的患者经早期腰池置管引流后症状即刻减轻,所有患者精神状态短期内明显好转;1例视力障碍患者引流2d后视力基本正常,仅有1例遗留有轻度视力障碍。最后痊愈4例,好转3例。治愈的4例患者均随访至今无复发。提示早期腰池置管引流能有效降低新型隐球菌脑膜炎颅内压,改善临床症状,为抗真菌治疗赢取时间。     

层状复合氢氧化物的药物控释动力学机制

以层状复合氢氧化物(LDH)为载体组装乙酰苯甲酸(ASP)的插层复合物LDH-ASP,以pH2.48~6.89的磷酸盐溶液为介质进行药物释放动力学实验,通过对不同时间药物释放度的测定及释放药物后载体结构变化分析研究了LDH对层间药物的控制释放机制。结果表明粉末状LDH-ASP能在较宽的pH范围表现明显缓控释作用,药物释放度积分方程与Higchi方程、Ritger-Peppas方程、Bhaskar方程及一级动力学方程等经验模型吻合。复合物与溶出介质的反应机制研究表明,药物释放速率及释放度大小取决于交换配比n(ASP)/n[HnPO4(3-n)-]所决定的LDH层间通道畅阻情况。     

1,3-双(2-取代硫醚-1,3,4-噁二唑-5-基)苯的合成及其杀菌活性

以间苯二甲酸二甲酯为起始原料,经酰肼化、关环和硫醚化反应合成了8个新型的1,3-双(2-取代硫醚-1,3,4-噁二唑-5-基)苯,其结构经1H NMR,MS和元素分析表征。初步的生物活性测试结果表明,部分化合物具有较好的杀菌活性。     

Prevalence of voice symptoms and risk factors in teacher students

Teacher students seem to have low awareness of the vocal demands in their future professions, and students with vocal symptoms are at risk for developing voice disorders during their professional careers. The purpose of the present study was to determine the prevalence of voice problems in teacher students at the very beginning of their education at the university. Of 1636 students approached in the first couple of days, 1250 (76%) answered two questionnaires about voice symptoms, Screen6 and Swedish Voice Handicap Index (Sw-VHI), and one questionnaire about potential risk factors. A majority of the students were women, and their mean age was 23 years (range, 18-52 years). The results showed that 208 of 1250 students (17%) had voice problems, defined as at least two symptoms weekly or more often in Screen6. The proportion of women was larger in the group with voice problems than in the group without voice problems. Significant risk factors for voice problems were vocal fold problems in childhood and adulthood, frequent throat infections, airborne allergy, smoking, hearing problems, previous work as teacher or leader, voice demanding hobbies, and previous speech therapy or voice training. There was a clear association between the number of potential vocal risk factors and the number of voice symptoms. There was also a strong association between the scores of the two questionnaires, the Sw-VHI and the Screen6. Students with voice problems according to Screen6 scored 23.1 (mean Sw-VHI) compared with 7.8 for students without voice problems.     

Advancing density functional theory to finite temperatures: methods and applications in steel design

The performance of materials such as steels, their high strength and formability, is based on an impressive variety of competing mechanisms on the microscopic/atomic scale (e.g. dislocation gliding, solid solution hardening, mechanical twinning or structural phase transformations). Whereas many of the currently available concepts to describe these mechanisms are based on empirical and experimental data, it becomes more and more apparent that further improvement of materials needs to be based on a more fundamental level. Recent progress for methods based on density functional theory (DFT) now makes the exploration of chemical trends, the determination of parameters for phenomenological models and the identification of new routes for the optimization of steel properties feasible. A major challenge in applying these methods to a true materials design is, however, the inclusion of temperature-driven effects on the desired properties. Therefore, a large range of computational tools has been developed in order to improve the capability and accuracy of first-principles methods in determining free energies. These combine electronic, vibrational and magnetic effects as well as structural defects in an integrated approach. Based on these simulation tools, one is now able to successfully predict mechanical and thermodynamic properties of metals with a hitherto not achievable accuracy.     

Reversal of atomic contrast in scanning probe microscopy on (111) metal surfaces

We study the origin of atomic contrast on Cu(111) and Pt(111) surfaces probed by a non-contact atomic force microscope and scanning tunnelling microscope. First-principles simulations of the interaction between the atoms of the scanning tip and those of the probed surface show a dependence of the resulting contrast on the tip-sample distance and reveal a close relation between contrast changes and relaxation of atomic positions in both the tip and the sample. Contrast reversion around the distance where the short-range attractive atomic force reaches its maximum is predicted for both types of microscopies. We also demonstrate a relation between the maximal attractive force in a F-z atomic force spectroscopy and the chemical identity of the apex atom on the imaging tip.     

Exchange bias in bulk layered hydroxylammonium fluorocobaltate (NH?OH)?CoF?

The magnetic properties of layered hydroxylammonium fluorocobaltate (NH(3)OH)(2)CoF(4) were investigated by measuring its dc magnetic susceptibility in zero-field-cooled (ZFC) and field-cooled (FC) regimes, its frequency dependent ac susceptibility, its isothermal magnetization curves after ZFC and FC regimes, and its heat capacity. Effects of pressure and magnetic field on magnetic phase transitions were studied by susceptibility and heat capacity measurements, respectively. The system undergoes a magnetic phase transition from a paramagnetic state to a canted antiferromagnetic state exhibiting a weak ferromagnetic behavior at T(C) = 46.5 K and an antiferromagnetic transition at T(N) = 2.9 K. The most spectacular manifestation of the complex magnetic behavior in this system is a shift of the isothermal magnetization hysteresis loop in a temperature range below 20 K after the FC regime-an exchange bias phenomenon. We investigated the exchange bias as a function of the magnetic field during cooling and as a function of temperature. The observed exchange bias was attributed to the large exchange anisotropy which exists due to the quasi-2D structure of the layered (NH(3)OH)(2)CoF(4) material.     

Magnetic order in hybrid frustrated magnets Gd(2-x)Tb(x)Ti2O7 (x = 0.2 and 0.5)

We report on the specific heat, magnetization and ac susceptibility measurements of single crystals of hybrid frustrated magnets Gd(1.8)Tb(0.2)Ti(2)O(7) and Gd(1.5)Tb(0.5)Ti(2)O(7). The analysis of experimental data revealed that, although partial replacing of the Gd(3+) ions by the Tb(3+) ions in the Gd(2)Ti(2)O(7) host lattice slightly enhances antiferromagnetic coupling, as inferred from the evolution of the paramagnetic Curie-Weiss temperature, the ordering temperature gradually decreases. Paramagnetic correlations introduced by the Tb(3+) ions cause this perturbation, altering the effective further neighbor interactions and destabilizing the ground state in Gd(2)Ti(2)O(7). In addition, the low-energy states of Gd(2-x)Tb(x)Ti(2)O(7) are suggested to possess a nature different from those in parent members Tb(2)Ti(2)O(7) and Gd(2)Ti(2)O(7). Finally, the frequency-dependent magnetic susceptibility behavior in Gd(1.5)Tb(0.5)Ti(2)O(7) is consistent with the formation of a spin-glass-like state indicating a pronounced slowing down of the dynamical response of the studied hybrid magnets.     

Magnetic properties and relaxation dynamics of a frustrated Ni? molecular nanomagnet

The Ni? nanomagnet represents an ideal model system for investigating the effects of geometrical frustration in magnetic interactions. The Ni ions in the magnetic core are arranged on two corner-sharing tetrahedra and interact through antiferromagnetic exchange couplings. We show that the high degree of frustration leads to a magnetic energy spectrum with large degeneracies which result in unusual static and dynamical magnetic properties. In particular, the relaxation dynamics of the magnetization is characterized by several distinct characteristic times. We also discuss the possible interest of Ni? for magnetocaloric refrigeration.     

Phonon-limited transport coefficients in extrinsic graphene

The effect of electron-phonon scattering processes on the thermoelectric properties of extrinsic graphene was studied. Electrical and thermal resistivity, as well as the thermopower, were calculated within the Bloch theory approximations. Analytical expressions for the different transport coefficients were obtained from a variational solution of the Boltzmann equation. The phonon-limited electrical resistivity ρ(e-ph) shows a linear dependence at high temperatures and follows ρ(e-ph) ~T(4) at low temperatures, in agreement with experiments and theory previously reported in the literature. The phonon-limited thermal resistivity at low temperatures exhibits a ~T dependence and achieves a nearly constant value at high temperatures. The predicted Seebeck coefficient at very low temperatures is Q(T) ~ Π(2)k(2)_(B)/T(3eE_(F), which shows a n(-1/2) dependence with the density of carriers, in agreement with experimental evidence. Our results suggest that thermoelectric properties can be controlled by adjusting the Bloch-Grüneisen temperature through its dependence on the extrinsic carrier density in graphene.