3,599 research outputs found
Review of Generalized Latent Variable Modeling by Skrondal and Rabe-Hesketh
No full textThe new book by Skrondal and Rabe-Hesketh (2004) is reviewed.GLLAMM, generalized linear latent and mixed models, latent variables
Ordered Nanostructures of a [2] Catenane Through Self-Assembly at Surfaces - An STM Study with Sub-Molecular Resolution
No full textSamori P, Jackel F, Ünsal Ö, Godt A, Rabe JP. Ordered nanostructures of a [2]catenane through self-assembly at surfaces - An STM study with sub-molecular resolution. ChemPhysChem. 2001;2(7):461-464
Flexible accumulation and depletion mode organic field effect transistors with tunable threshold voltage
No full textIn this paper we report on the possibility to use organic bulk heterojunctions of two derivatives of a conjugated molecule for tuning and controlling charge carrier population and transport within the active layer. In particular, we report on the fabrication and operation of a series of OFETs, which exhibit (i) accumulation and depletion mode operation, (ii) wide tunability of threshold voltage, (iii) mechanical flexibility. We fabricated OFETs on plastic substrates (Mylar®), acting at the same time as gate dielectric, by co-depositing two organic semiconductor materials, sexithiophene (6T) and α, ω-dihexylsexithiophene (DH6T), at various ratios. Despite the identical conjugated moiety, the two materials gave rise to a very different electrical behaviour, OFETs comprising pure 6T channels exhibited a slightly negative threshold voltage (VT), thus working in p-type accumulation mode. When only DH6T formed the channel, large positive V T was observed, giving evidence that an accumulation of p-type charge carriers was already present without applying any gate bias and that these OFETs work in the depletion regime. DH6T has a 0.15 eV lower ionization energy than 6T, consequently, DH6T is more easily p-doped by atmospheric oxygen than 6T, explaining why pure DH6T OFETs exhibit depletion mode operation (heavily doped) and pure 6T ones are accumulation type (intrinsic). As a result, for OFETs with mixed 6T:DH6T channels we found a linear dependence of VT on the 6T: DH6T ratio. Moreover, the hole mobility was essentially constant for all mixing ratios. 6T and DH6T co-deposited films have very similar structural and morphological properties as the pure materials films, and the two molecules form intercalation compounds. Our work is particularly interesting because it demonstrates the possibility to adjust the device working point and tune its operational mode without negatively affecting charge carriers transport across the channel. A rational approach to precisely control OFET performance has thus been established. Moreover, this approach is not influenced by the particular substrate employed as gate dielectric, and it is therefore suitable for tuning the electrical properties in flexible plastic devices, providing a considerable extension of organic electronics application-potentia
Flexible accumulation and depletion mode organic field effect transistors with tunable onset-voltage
No full textThe emerging appealing possibility of exploiting organic heterojunctions for obtaining new electronics properties derived from the interface between different semiconductors is going to add a further degree of freedom for improving OFET performances. In this paper we report on the possibility to use organic bulk heterojunctions of two derivatives of a conjugated molecule for tuning and controlling charge carrier population and transport within the active layer. In particular, we report on the fabrication and operation of a series of OFETs, which exhibit (i) accumulation and depletion mode operation, (ii) wide tunability of threshold voltage, (iii) mechanical flexibility.
We fabricated OFETs on plastic substrates (Mylar®), acting at the same time as gate dielectric, by co-depositing two organic semiconductor materials, sexithiophene (6T) and α,ω-dihexylsexithiophene (DH6T), at various ratios. OFETs comprising pure 6T channels exhibited a slightly negative threshold voltage (VT), thus working in p-type accumulation mode. When only DH6T formed the channel, large positive VT was observed, giving evidence that an accumulation of p-type charge carriers was already present without applying any gate bias and that these OFETs work in the depletion regime. Photocurrent spectroscopy measurements confirmed that a larger concentration of charge carriers is present in DH6T OFETs.
For OFETs with mixed 6T:DH6T channels we found a linear dependence of VT on the 6T: DH6T ratio. Moreover, the hole mobility was essentially constant for all mixing ratios (≥ 5x10-3 cm2/Vs), and even higher than for pure 6T flexible OFETs (3x10-3 cm2/Vs). X-ray diffraction and atomic force microscopy studies showed that 6T and DH6T co-deposited films (on Mylar® and Si-oxide) have very similar structural and morphological properties as the pure materials films, and that the two molecules form intercalation compounds. This is particularly interesting because it demonstrates the possibility to adjust the device working point and tune its operational mode without negatively affecting charge carriers transport across the channel.
Our work shows that extremely wide OFET function tunability can be achieved by combining molecules with appropriately adjusted properties in molecularly mixed films. A rational approach to precisely control OFET performance has thus been established, providing a considerable extension of the application-potential of organic electronics
The Rabe amination after a century: Direct addition of N-heterocycles to carbonyl compounds
No full textA catalytic version of the Rabe electrophilic amination is presented. This kind of reaction was originally employed in 1918 in a key step for the conversion of quinotoxine to quinine. Ketones and α-substituted aldehydes give the corresponding α-aminated carbonyl compounds in moderate yield. α,α-Unsubstituted aldehydes give rise to amino ketones via a novel rearrangement. © 2012 The Royal Society of Chemistry
CALCULATION OF MONOLAYER STRUCTURES OF HYDROCARBON CHAINS ON TRANSITION-METAL DICHALCOGENIDES - DOTRIACONTANE ON MOSE2
No full textDissertatio Academica Quid Muhammedani De Christo Sentiant
No full textDISSERTATIO ACADEMICA QUID MUHAMMEDANI DE CHRISTO SENTIANT
Dissertatio Academica Quid Muhammedani De Christo Sentiant ([1])
Title page ([1])
In Sacram Regiam Majestatem Magnæ Fidei Viro, Frederico Dalman, Cubiculario Regio S. P. D. Casten Rabe. ([2])
§. I. ([3])
§. II. (4)
§. III. (5)
§. IV. (9)
§. V. (11)
§. VI. (13
Remodeling of bronchial and pulmonary muscular arteries in mild/moderate COPD
No full textPulmonary hypertension is well documented in severe COPD but little is known about vascular remodeling in mild/moderate patients. Aim:To investigate bronchial and pulmonary muscular arteries morphology and the expression of elastic fibers (EF) and collagen I in the lungs of mild/moderate COPD patients. Methods:Lung tissue of 18 COPD subject (FEV1:67±15%pred), 14 non-obstructed smokers(NOS) (FEV1:95±10%pred) and 11 never-smoking controls(CTRL) (FEV1:108±15%pred) was used to analyze the morphology of bronchial and pulmonary muscular arteries and the expression of EF and collagen I in the tunica intima, media and adventitia, using immune- and histochemistry and image analysis. Values (mean±SD) were expressed as (stained) area⁄vessel outer perimeter (μm2⁄μm) and as staining density (collagen I). Results:The intimal areas of pulmonary (CTRL=8.87±4.3, COPD=14.7±5, p=0.04) and the adventitia of bronchial arteries (CTRL=27.7±11.4, COPD=50.6±23.7, p=0.007) were larger in COPD patients than in CTRL. Higher EF expression was observed in adventitia of bronchial arteries of NOS group (8.8±13.2) than CTRL (3.1±1.3, p=0.04). The CTRL group had higher collagen I staining density in the adventitia of bronchial (CTRL=81.6±35.8; NOS=32.8±15; COPD=40.9±25.4, p=0.002) and pulmonary (CTRL=96.5±23.2; NOS=54.8±24; COPD=69.6±19.1, p=0.0005) arteries than NOS and COPD. Within COPD group, negative correlations were observed between the intimal area of pulmonary arteries and FEV1 (R=-0.57, p=0.04) and FEV1⁄FVC (R=-0.56, p=0.04). Conclusions:Remodeling of bronchial and pulmonary muscular arteries occurs in mild⁄moderate COPD, is associated with impaired lung function and it might contribute to the development of pulmonary hypertension
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