Tunable switching dynamics of a single Si dopant in GaAs(110)

The dynamic behavior of single bistable Si dopants in the GaAs (110) surface, which switch between a positive and a negative charge configuration, was investigated using a scanning tunneling icroscope (STM) and noise analysis electronics. The dopant atom switching frequency shows a clear dependence on the bias voltage and tunneling current, because these parameters influence the escape and capture processes of electrons. Our physical model for these processes, taking into account the relevant tunneling barriers, matches well with the experimental data. By choosing the appropriate tunneling conditions, we show that a single dopant can be employed as a memory element. The STM tip serves both as an electrical gate to write and as a probe to read the information stored on a single Si atom

Tunable switching dynamics of a single Si dopant in GaAs(110)

The dynamic behavior of single bistable Si dopants in the GaAs (110) surface, which switch between a positive and a negative charge configuration, was investigated using a scanning tunneling icroscope (STM) and noise analysis electronics. The dopant atom switching frequency shows a clear dependence on the bias voltage and tunneling current, because these parameters influence the escape and capture processes of electrons. Our physical model for these processes, taking into account the relevant tunneling barriers, matches well with the experimental data. By choosing the appropriate tunneling conditions, we show that a single dopant can be employed as a memory element. The STM tip serves both as an electrical gate to write and as a probe to read the information stored on a single Si atom

Polypeptid-Tag's fuer den Nachweis und die Aufreinigung von Polypeptiden

EP 1092769 A UPAB: 20010522 NOVELTY - Polypeptide with tag sequence (I) or a sequence derived from (I) by replacement of one or more amino acids (aa), provided the three-dimensional/tertiary structure remains essentially unchanged, is new. DETAILED DESCRIPTION - Polypeptide having the tag sequence KDWEHL (I) or a sequence derived from it by replacement of one or more amino acids (aa), provided the three-dimensional/tertiary structure remains essentially unchanged. INDEPENDENT CLAIMS are also included for the following: (1) expression vector encoding a fusion protein (FP) of a target polypeptide (II) and (I); (2) FP encoded by the vector of (1); (3) antibodies (Ab), or their fragments, directed against (I); and (4) kit containing the vector of (1) and optionally Ab. USE - (I) are used for isolation and/or detection of fusion polypeptides that contain (I), by reaction with (I)-specific antibodies (Ab). Ab are used for isolation, purification and/or detection of polypeptides (also for determination of molecular weight, cell localization, post-translational modification and interaction with other factors), and for diagnosis of infection by tobacco mosaic virus (TMV). ADVANTAGE - (I) is recognized by very specific, high-affinity antibodies that do not cross-react significantly with other cellular proteins (bacterial or eukaryotic)

Evolution of the Macondo Well Blowout: Simulating the Effects of the Circulation and Synthetic Dispersants on the Subsea Oil Transport

During the Deepwater Horizon incident, crude oil flowed into the Gulf of Mexico from 1522 m underwater. In an effort to prevent the oil from rising to the surface, synthetic dispersants were applied at the wellhead. However, uncertainties in the formation of oil droplets and difficulties in measuring their size in the water column, complicated further assessment of the potential effect of the dispersant on the subsea-to-surface oil partition. We adapted a coupled hydrodynamic and stochastic buoyant particle-tracking model to the transport and fate of hydrocarbon fractions and simulated the far-field transport of the oil from the intrusion depth. The evaluated model represented a baseline for numerical experiments where we varied the distributions of particle sizes and thus oil mass. The experiments allowed to quantify the relative effects of chemical dispersion, vertical currents, and inertial buoyancy motion on oil rise velocities. We present a plausible model scenario, where some oil is trapped at depth through shear emulsification due to the particular conditions of the Macondo blowout. Assuming effective mixing of the synthetic dispersants at the wellhead, the model indicates that the submerged oil mass is shifted deeper, decreasing only marginally the amount of oil surfacing. In this scenario, the oil rises slowly to the surface or stays immersed. This suggests that other mechanisms may have contributed to the rapid surfacing of oil-gas mixture observed initially. The study also reveals local topographic and hydrodynamic processes that influence the oil transport in eddies and multiple layers. This numerical approach provides novel insights on oil transport mechanisms from deep blowouts and on gauging the subsea use of synthetic dispersant in mitigating coastal damage