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Abstract: We used photocurrent spectroscopy to study the electronic density of states distribution in thin films of sexithiophene and an alkylated analog, both at the band edge and inside the band-gap. The presented photocurrent spectroscopy analyses provide direct experimental evidence for a modification of the distribution of the electronic density of states in an organic field effect transistor (OFET) channel induced by the modulation of the effective carrier density by the gate voltage. We observe a correlation between a gate voltage induced increase of the carrier density in the channel and a broadening of the distribution of the electronic states around the band edge. We also detected the formation of deep electrically active states within the band-gap of sexithiophene OFETs, induced by the exposure to air and light. These results are in good agreement with the evolution of the macroscopic transport parameters of the devices, i.e., carrier mobility and threshold voltage, as a function of the exposure time to light and atmosphere. [Copyright &y& Elsevier]

Photocurrent (PC) spectroscopy is proposed as a reliable tool in the investigation of the transport properties of organic thin-film transistors (OFETs). We have applied PC analyses to the study of the electronic density of states (DOS) distribution of the OFETs with crystalline-mixed films of two derivatives of a conjugated molecule [ α-sexithiophene (6T), and its alkylated analogue α, ω-dihexylsexithiophene (DH6T)] as the active semiconductor. We have investigated the modifications in the DOS distribution associated to variations in the carrier density in the OFET channel and we have detected the formation of deep electrically active states in the below-band-gap region, associated to polaron states induced by a prolonged exposure of the device to atmosphere. A clear correlation between the PC results and the electrical characteristics of the corresponding FET devices has been observed. [ABSTRACT FROM AUTHOR]

Abstract: We studied the anisotropic charge transport properties of solution-grown organic single crystals based on a dipolar molecule (4-hydroxy-cyanobenzene) by field effect devices and by spectral photocurrent analyses. Optical excitation differently affects the flow of charge carriers along the two main planar crystal axes, altering the charge transport anisotropy induced by the molecular π-orbitals stacking. We attribute this behaviour to the presence of an intrinsic molecular dipole and to its different orientation within the crystal lattice and we advance a hypothesis on the nature of the observed band of deep trapping states. [Copyright &y& Elsevier]

Thermomagnetic measurements are used to obtain the size distribution and anisotropy of magnetic nanoparticles. An analytical transformation method is described which utilizes temperature-dependent zero-field cooling magnetization data to provide a quantitative measurement of the average diameter and relative abundance of superparamagnetic nanoparticles. Applying this method to self-assembled MnAs nanoparticles in MnAs–GaAs composite films reveals a log-normal size distribution and reduced anisotropy for nanoparticles compared to bulk materials. This analytical technique holds promise for rapid assessment of the size distribution of an ensemble of superparamagnetic nanoparticles. [ABSTRACT FROM AUTHOR]

Nonvolatile resistive memory consisting of gold nanoparticles embedded in the conducting polymer poly(4-n-hexylphenyldiphenylamine) examined using admittance spectroscopy. The frequency dependence of the devices indicates space-charge-limited transport in the high-conductivity “on” state, as well as evidence for similar transport in the lower-conductivity “off” state. Furthermore, the larger dc capacitance of the on state indicates that a greater amount of filling of the midgap nanoparticle trap levels increases the overall device conductivity, leading to the memory effect. [ABSTRACT FROM AUTHOR]

Provides information on a study that examined light emitting diodes made with poly(2-methoxy-5(2'ethyl)-hexoxy-phenylenevinylene) using indium-tin-oxide as anode and Ca as cathode as they age during operation in a dry inert atmosphere. Experimental procedure; Results and discussion on the study; Conclusions.

The objective of this study was to determine the disposition of ampicillin in plasma, uterine tissue, lochial fluid, and milk of postpartum dairy cattle. Ampicillin trihydrate was administered by intramuscular (i.m.) injection at a dose of 11 mg/kg of body weight every 24 h ( n = 6, total of 3 doses) or every 12 h ( n = 6, total of 5 doses) for 3 days. Concentrations of ampicillin were measured in plasma, uterine tissue, lochial fluid, and milk using HPLC with ultraviolet absorption. Quantifiable ampicillin concentrations were found in plasma, milk, and lochial fluid of all cattle within 30 min, 4 h, and 4 h of administration of ampicillin trihydrate, respectively. There was no significant effect of dosing interval (every 12 vs. every 24 h) and no significant interactions between dosing interval and sampling site on the pharmacokinetic variable measured or calculated. Median peak ampicillin concentration at steady-state was significantly higher in lochial fluid (5.27 μg/mL after q 24 h dosing) than other body fluids or tissues and significantly higher in plasma (3.11 μg/mL) compared to milk (0.49 μg/mL) or endometrial tissue (1.55 μg/mL). Ampicillin trihydrate administered once daily by the i.m. route at the label dose of 11 mg/kg of body weight achieves therapeutic concentrations in the milk, lochial fluid, and endometrial tissue of healthy postpartum dairy cattle. [ABSTRACT FROM AUTHOR]

Ultrahigh storage densities can be achieved by using a thermomechanical scanning-probe-based data-storage approach to write, read back, and erase data in very thin polymer films. High data rates are achieved by parallel operation of large twodimensional arrays of cantilevers that can be batch fabricated by silicon-surface micromachining techniques. The very high precision required to navigate the storage medium relative to the array of probes is achieved by microelectromechanical system (MEMS)-based x and y actuators. The ultrahigh storage densities offered by probe-storage devices pose a significant challenge in terms of both control design for nanoscale positioning and read-channel design for reliable signal detection. Moreover, the high parallelism necessitates new dataflow architectures to ensure high performance and reliability of the system. In this paper, we present a small-scale prototype system of a storage device that we built based on scanning-probe technology. Experimental results of multiple sectors, recorded using multiple levers at 840 Gb/in² and read back without errors, demonstrate the functionality of the prototype system. This is the first time a scanning-probe recording technology has reached this level of technical maturity, demonstrating the joint operation of all building blocks of a storage device. [ABSTRACT FROM AUTHOR]