RESUMEN
We present the construction and performance of an ultra-low-temperature scanning tunneling microscope (STM), working in ultra-high vacuum (UHV) conditions and in high magnetic fields up to 9 T. The cryogenic environment of the STM is generated by a single-shot 3He magnet cryostat in combination with a 4He dewar system. At a base temperature (300 mK), the cryostat has an operation time of approximately 80 h. The special design of the microscope allows the transfer of the STM head from the cryostat to a UHV chamber system, where samples and STM tips can be easily exchanged. The UHV chambers are equipped with specific surface science treatment tools for the functionalization of samples and tips, including high-temperature treatments and thin film deposition. This, in particular, enables spin-resolved tunneling measurements. We present test measurements using well-known samples and tips based on superconductors and metallic materials such as LiFeAs, Nb, Fe, and W. The measurements demonstrate the outstanding performance of the STM with high spatial and energy resolution as well as the spin-resolved capability.
RESUMEN
We present the design, setup, and operation of a new dip-stick scanning tunneling microscope. Its special design allows measurements in the temperature range from 4.7 K up to room temperature, where cryogenic vacuum conditions are maintained during the measurement. The system fits into every (4)He vessel with a bore of 50 mm, e.g., a transport dewar or a magnet bath cryostat. The microscope is equipped with a cleaving mechanism for cleaving single crystals in the whole temperature range and under cryogenic vacuum conditions. For the tip approach, a capacitive automated coarse approach is implemented. We present test measurements on the charge density wave system 2H-NbSe2 and the superconductor LiFeAs which demonstrate scanning tunneling microscopy and spectroscopy data acquisition with high stability, high spatial resolution at variable temperatures and in high magnetic fields.
RESUMEN
According to its aromatic nitro group acetylaminonitropropoxybenzene (Falimint) can be determined polarographically. The typical behavior of the nitro group becomes evident by the elektrochemical reduction. The investigation has shown two phases of reduction with pH-depended half-wave-potential shifts, so that a two-step mechanism is conceivable. Using direct current polarography the substance is determined in a concentration range from 1 to 100 micrograms/ml. Low elektroaktive background signals within the potential range the four-electron reduction step are the basis for the determination of the active agent in saliva, urine and blood plasma without any extracting procedures. It is possible to identify the substance by means of oscilloand square-wave-polarography. The resulting polarogrammes are typically for the p-nitrophenyl structure. Further a new quantitativ polarographic method, named sample-DC-polarography on the stationary mercury electrode is discussed for the determination of Falimint in blood plasma without any steps of separation and cleaning in the concentration range of 0,1-3,0 micrograms/ml.
Asunto(s)
Acetanilidas/metabolismo , Biofarmacia , Líquidos Corporales/análisis , Difusión , Humanos , Concentración de Iones de Hidrógeno , Cinética , Oxidación-Reducción , PolarografíaRESUMEN
The antitumor activity of titanocene dihalides (C5H5)2TiX2 with X=F, Cl, Br, I, NCS is investigated against Ehrlich ascites tumor in CF 1 mice. Varying doses of the compounds are applied as single i.p. injections 24 h p.t.t. both in non-buffered (pH 1.4-3.9) and buffered (pH 4.2-5.9) solutions or suspensions, all of the substances achieving in optimum doses cure rates of 100% on day 120 p.t.t. This corresponds to I.L.S. values of 600-750% referred to the untreated controls. Some drug-induced side effects, especially the appearance of postperitonitic symptoms several weeks after i.p. application of higher doses of titanocene dihalides, are strikingly reduced by pH elevation in the injected drug solutions.
Asunto(s)
Carcinoma de Ehrlich/tratamiento farmacológico , Compuestos Organometálicos/uso terapéutico , Titanio/uso terapéutico , Animales , Tampones (Química) , Relación Dosis-Respuesta a Droga , Femenino , Concentración de Iones de Hidrógeno , Ratones , Trasplante de Neoplasias , Compuestos Organometálicos/efectos adversos , Titanio/efectos adversosRESUMEN
The antitumor activity of molybdocene dichloride is tested against Ehrlich ascites tumor in CF1 mice. The application of 75 of 100 mg/kg 24 h after transplantation achieves 100% tumor inhibition until day 30. Following the d0 and d1 metallocene dichlorides of titanium and vanadium, molybdocene dichloride is the first analogous d2 system revealing similar antineoplastic properties.