Über den Einfluß oberflächenaktiver Anionen und Kationen auf Halogensilbersole und photographische Emulsionen. I

Ohne ZusammenfassungUnter Benutzung der Dissertation von R. Steudel (Dresden 1937).     

Interactions and reactions of transition metal clusters with the interior of single-walled carbon nanotubes imaged at the atomic scale

Clusters of transition metals, W, Re, and Os, upon encapsulation within a single-walled carbon nanotube (SWNT) exhibit marked differences in their affinity and reactivity with the SWNT, as revealed by low-voltage aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM). Activated by an 80 keV electron beam, W reacts only weakly with the SWNT, Re creates localized defects on the sidewall, and Os reacts readily causing extensive defect formation and constriction of the SWNT sidewall followed by total rupture of the tubular structure. AC-HRTEM imaging at the atomic level of structural transformations caused by metal-carbon bonding of π- and σ-character demonstrates what a crucial role these types of bonds have in governing the interactions between the transition metal clusters and the SWNT. The observed order of reactivity W < Re < Os is independent of the metal cluster size, shape, or orientation, and is related to the metal to nanotube bonding energy and the amount of electronic density transferred between metal and SWNT, both of which increase along the triad W, Re, Os, as predicted by first-principles density functional theory calculations. By selecting the appropriate energy of the electron beam, the metal-nanotube interactions can be controlled (activated or precluded). At an electron energy as low as 20 keV, no visible transformations in the nanotube in the vicinity of Os-clusters are observed.     

Functional MR imaging in the awake monkey: effects of motion on dynamic off-resonance and processing strategies

Functional MR imaging of the alert, behaving monkey is being used more and more often to detect activation patterns and guide electrophysiological research investigating the neural basis of behavior. Several labs have reported fMRI data from the awake monkey, but none of them has studied and systematically corrected the effects of monkeys' motion on fMRI time series. In this study, a significant refinement of acquisition and correction strategies is reported that can be used to minimize magnetic susceptibility artifacts induced by respiration and by jaw and body movement. Real-time acquisition of sensor signals (e.g., signals induced by jaw and body movement) and MR navigator data were combined to optimize fMRI signal-correction strategies. Within trials, the artifact-induced off-resonance changes were small and mainly reflected the effects of respiration; between trials, movements caused major changes of global frequency and shim (>20 Hz/cm). Several methods were used to assess the stability of the fMRI series: k-space analysis ('dynamic intensity and off-resonance changes in k-space', dubbed DICK and DORK) and image analysis using a Laplace operator and a center-of-mass metric. The variability between trials made it essential to correct for inter-trial variations. On the other hand, images were sufficiently stable with our approach to perform fMRI evaluations on single trials before averaging of trials. Different motion correction strategies were compared: DORK, McFLIRT (rigid body model with three translations and three rotations) and 2D image alignment based on a center-of-mass detection (in-plane translation). The latter yielded the best results and proved to be fast and robust for intra- and inter-trial alignment. Finally, fMRI in the behaving monkey was tested for spatial and temporal reproducibility on a trial-to-trial basis. Highly activated voxels also displayed good reproducibility between trials. On average, the BOLD amplitude response to a short 3-s visual stimulus was close to 2%.     

Status of the chiral magnetic effect and collisions of isobars

In this review, we examine the current theoretical and experimental status of the chiral magnetic effect.We discuss possible future strategies for resolving uncertainties in interpretation including recommendations for theoretical work, recommendations for measurements based on data collected in the past five years, and recommendations for beam use in the coming years of RHIC. We specifically investigate the case for colliding nuclear isobars(nuclei with the same mass but different charge) and find the case compelling. We recommend that a program of nuclear isobar collisions to isolate the chiral magnetic effect from background sources be placed as a high priority item in the strategy for completing the RHIC mission.     

Second harmonic generation: the solution for an amplitude-modulated initial pulse

We address the initial value problem for one-dimensional second harmonic generation starting from a purely amplitude-modulated fundamental wave. A general method to solve the problem in terms of a Schrödinger equation is presented, in which the initial pulse-shape is taken as a potential. Several examples with the complete solution given in analytical form are discussed. A much broader class of solutions can be found with the help of a single numerical integration. In particular, solutions with incident pulses approximating a sech -shape have been obtained.     

Structural ordering versus energy band alignment: Effects of self-assembled monolayers on the metal/semiconductor interfaces of small molecule organic thin-film transistors

A model describing the influence of self-assembled monolayers on the contact resistance of bottom-contact organic thin-film transistors is presented. The model takes the contact geometry, the energy level alignment and the structural order of the organic films into consideration when describing the contact effects of organic transistors. The treatment of the metal source/drain electrodes of the transistors by self-assembled monolayers allows for tuning the work function of the metal contact and an improved ordering of the organic molecules on top of the source/drain contacts. The results reveal that the contact resistance is mainly determined by the molecular ordering, rather than the tuning of the work function. The model is compared to experimentally measured contact resistances for different self-assembled monolayers.     

New Titanocene Complexes [Cp2Ti(μ-S2)2NR] (with R = Me and n Oct) as Transfer Reagents for the Synthesis of the Heterocycles S5NR and S6NR

The reaction of 1,4-S₄(NR)₂ with (η⁵-C₅H₅)₂Ti(CO)₂ yields [C_p2Ti(μ-S₂)₂NR] which on treatment with SCl₂ or S₂Cl₂ provides the novel heterocycles S₅NR and S₆NR (R = Me, Oct).     

Low-temperature and scalable complementary thin-film technology based on solution-processed metal oxide n-TFTs and pentacene p-TFTs

In this work, a completely scalable integration process is presented for organic–inorganic complementary logic, based on low-temperature spin-coated n-type metal oxide TFTs and thermally evaporated p-type pentacene TFTs. Both transistor types are photolithographically processed side-by-side, without the use of any shadow mask. High performance n-type metal oxide TFTs, post-annealed at a maximum temperature of only 250 °C, exhibit saturation mobilities exceeding 2 cm²/(V s), subthreshold swing as low as 0.19 V/decade and I_on/I_off ratios beyond 10⁷ after integration with p-type pentacene TFTs. Using this hybrid complementary technology, 5-stage and 19-stage ring-oscillators are demonstrated, operating at supply voltages as low as 2.5 V. The ring-oscillators oscillate at a frequency of more than 110 kHz, corresponding to stage delays as low as 0.74 μs, at a supply bias of 20 V.     

Intelligent sensor system for CO2 partial pressure measurements

Solid state electrochemical gas sensors allow the measurement of partial gas pressures with high accuracy. However, there are problems related to the response time, drift and cross sensitivity which should be solved to improve the performance of these sensors. An intelligent sensor system is presented which improves the sensor response time, compensates the drift and allows to calculate functional relationships between the electrical and the chemical energy of galvanic cell reactions. An electronic circuit for evaluating the measured cell voltage of a type III potentiometric CO₂ sensor is also presented.