Polychromatic reflectance and transmittance of a slab with a randomly rough boundary

We investigated four different approximation models for describing the polychromatic reflectance and transmittance of a slab with a randomly rough boundary while taking into account the coherent and the incoherent scattering of the rough boundary. Comparisons with experiments (an etched-silicon wafer) show that approximation models that apply a two-scale roughness to the randomly rough boundary and that take into account the coherent and the incoherent scattering yield better agreement and extend the range of validity of the approximation to shorter wavelengths.     

Polarized resonance Raman spectroscopy of fully-oriented crystalline trans-(CH)x

Fully-oriented non-fibrous crystalline trans-(CH)_x films prepared by stress-orientation and conversion of poly-7,8-bis-(trifluoromethyl)-tricyclo-{4.2.2.0.}-deca-3,7,9,-triene, poly-(BTFM-TCDT), are investigated by polarized resonance Raman spectroscopy. With an excitation wavelength of 647.1 nm and parallel polarization (parallel to the c-axis, i.e., the stretching direction), two strong Raman bands are observed at 1078 cm^?1 and 1469 cm^?1, whereas for perpendicular polarization, no Raman scattered light can be detected. This polarization behaviour proves the perfect alignment of long unperturbed conjugated sequences parallel to the c-axis.Upon excitation with blue laser light ($\text{λ}{}_{\mathrm{<mtext>l</mtext>}}\text{= 457.9}\text{nm}$), for which preferentially short conjugated sequences come into resonance, an increase of the depolarization ratio compared to the red excitation is observed.These results are discussed in terms of conjugation length distributions and resonance conditions with respect to the polarized optical absorption spectra.     

The letter of recommendation effect in informant ratings of personality.

In most studies using informant reports of personality, the informants are recruited by the targets. Such informants may tend to like the targets and thus portray them in specific ways (e.g., too positively). Study 1 (N = 403) demonstrated the necessity to distinguish between “liking” and “knowing” in studying the relationships between informants and targets. Informants who liked their targets better described them more positively (i.e., as being more extraverted, agreeable, open, conscientious, and less neurotic). The association between personality ratings and liking was moderated by item evaluativeness. Liked targets were also described as being more similar to each other (range restriction), which would lower correlations of informant ratings of personality with external variables. Study 2 (N = 90) used a within-subjects design to disentangle actual personality differences between targets (substance) from the informants’ specific views on the targets (style). Ninety informants were asked to nominate targets they did not like. These targets then nominated informants of their own choice. Target-nominated informants liked the targets very much and described the targets’ personalities very positively and in ways that were highly redundant with the average target’s self-rating. There was evidence that lower liking may be associated with better accuracy. Higher subjective levels of knowing were not associated with better interrater agreement but with a greater willingness to describe targets negatively. Implications for the field of recruiting are discussed. Where possible, the choice of informants and referees should be made independent of the targets’ preferences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Efficient color tuning (blue, red-orange, white) of light emitting diodes by excitation energy transfer

We present a color tuning technique allowing to control the emission colors of polymer light emitting diodes (PLEDS), which is of considerable interest for flat panel display applications. The emission color variation of the PLED from blue to red-orange is achieved by blending small amounts of a red light emitting guest polymer with the active PLED layer consisting of a blue emitting laddertype poly (paraphenylene) (LPPP). Using this new technique we realized highly efficient stable single layer PLEDs emitting different colors including white light emission. Besides the color tuning, which is established by an efficient excitation energy transfer (EET) and charge transfer from the host, m-LPPP, to the guest polymer, a significant increase of the photoluminescence (PL) and the electroluminescence (EL) quantum efficiency is observed.     

The Influence of the Phase Morphology on the Optoelectronic Properties of Light‐Emitting Electrochemical Cells

We report on the morphological aspects of thin films prepared from a blue–green light‐emitting conjugated polymer, (methyl‐substituted ladder‐type poly(p‐phenylene, mLPPP)), blended with a solid‐state electrolyte composed either by a crown ether, dicyclohexano‐18‐crown‐6 (DCH18C6), or a high‐molecular‐weight poly(ethylene oxide) (HMWPEO), and a Li salt, lithium trifluoromethanesulfonate (LiCF₃SO₃, Li triflate (LiTf)), as they have been successfully applied in light‐emitting electrochemical cells (LECs). The surface morphologies of the blend layers were investigated using atomic force microscopy (AFM) in tapping mode, and the ion distribution was probed using X‐ray analysis by means of energy‐dispersive X‐ray spectrometry (EDXS) in the scanning electron microscope (SEM). We show that the two different phase‐separation processes, the complexation tendencies of the ionic species as well as the ionic transport numbers, have tremendous influence on the performances of the corresponding LECs, revealing either rectifying or symmetric optoelectronic characteristics in forward and reverse bias directions. This opens up new possibilities for tuning the optoelectronic properties of ion‐supported organic electronic devices.     

Efficient charge carrier transfer from m-LPPP to C60 derivatives

The improvement of dissociation of singlet excitons by electron or hole capturing species like C₆₀ is essential for efficient photovoltaic cells based on conjugated systems. We investigate the charge transfer in blends of methyl-substituted ladder type poly-(paraphenylene) (m-LPPP) with new well soluble C₆₀ derivatives, which are characterized by sidegroups of different electronic properties (donor, acceptor nature). It is shown, that the electronic properties of the C₆₀ sidegroups strongly influence the efficiency of the charge transfer in these blends and hence significant different behaviours in the photocurrent and photoinduced absorption is observed.     

Magnetic susceptibility studies on PrxY1-xBa2Cu3O7- delta single crystals in the insulating regime

During the dissection of the neck region of a 56 year old female cadaver an artery was found branching from the thyrocervical trunk as a fourth branch and entering the aortic arch on its superior posterior aspect between the brachiocephalic trunk and the left common carotid artery. Selective angiography revealed that this artery branched into several arterioles at its junction on the superior aspect of the aortic arch between the brachiocephalic trunk and the left common carotid artery. No similar structure could be found in the literature. Evaluation of this phenomenon according to our knowledge of the development of human arterial networks, it was concluded that the artery might be a persistent intersegmental artery, or an enlarged nutrient artery (vas vasorum) to the aortic arch.