Asymmetric Injection in Organic Transistors via Direct SAM Functionalization of Source and Drain Electrodes

The fabrication of organic optoelectronic devices integrating asymmetric electrodes enables optimal charge injection/extraction at each individual metal/semiconductor interface. This is key for applications in devices such as solar cells, light-emitting transistors, photodetectors, inverters, and sensors. Here, we describe a new method for the asymmetric functionalization of gold electrodes with different thiolated molecules as a viable route to obtain two electrodes with drastically different work function values. The process involves an ad hoc design of electrode geometry and the use of a polymeric mask to protect one electrode during the first functionalization step. Photoelectron yield ambient spectroscopy and X-ray photoelectron spectrometry were used to characterize the energetic properties and the composition of the asymmetrically functionalized electrodes. Finally, we used poly(3-hexylthiophene)-based organic thin-film transistors to show that the asymmetric electronic response stems from the different electronic structures of the functionalized electrodes

Competing bubble formation mechanisms in rigid polyurethane foaming

This study investigates the influence of air bubbles inclusion on the foaming of water blown and water-pentane blown rigid polyurethane and polyisocyanurate foams. It was observed that, when a large number of air bubbles were included in the reacting system during the mixing stage (fast mixing), no further bubble nucleation from water reaction or pentane evaporation occurred. In this case, foam morphology was solely dictated by the mixing stage and by later bubble coarsening. Instead, when no air bubbles were included during mixing (slow mixing), nucleation of new bubbles from CO2 (from water-isocyanate reaction) and pentane was observed. Furthermore, both bubble coalescence and Ostwald ripening were observed as mechanisms responsible for the foam morphology coarsening, the latter being less effective in the case of polyisocyanurate foams

The effect of organofluorine additives on the morphology, thermal conductivity and mechanical properties of rigid polyurethane and polyisocyanurate foams

This study investigates the effect of liquid-type organofluorine additives (OFAs) on the morphology, thermal conductivity and mechanical properties of rigid polyurethane (PU) and polyisocyanurate (PIR) foams. Foams were characterized in terms of their morphology (density, average cell size, anisotropy ratio, open cell content), thermal conductivity and compressive as well as flexural properties. Based on the results, we observed that OFAs efficiently reduced the average cell size of both PU and PIR foams, leading to improved thermal insulating and mechanical properties

Microcellular Thermosetting Polyurethane Foams

Thermosetting polyurethane foams are nowadays produced with typical bubble size, d > 150 μm, with plenty of room for improvement towards the cellular structure refinement, to gain, among others, in the thermal insulation performances. We herein report a first example of a microcellular thermosetting polyurethane foam, i. e. with bubble size below 5 μm, produced via the gas foaming technology. In particular, high-pressure CO2, N2 and their mixtures were utilized as blowing agents: solubilized separately into the polymer precursors, they were brought into a supersaturated state by a pressure reduction to induce the bubble nucleation and growth. To achieve microcellular foams, we made use of a novel two-stage pressure reduction program, concurrent to the polymer curing. The first stage is a pressure quench O (10-2 s) from the saturation pressure to an intermediate pressure to induce the nucleation of a large amount of dense bubbles. The second stage is a slow O (102 s) further pressure decrease to ambient pressure, allowing for a slow bubble growth, designed to reach ambient pressure exactly when the curing reached completion

Light-enhanced liquid-phase exfoliation and current photoswitching in graphene-azobenzene composites

Multifunctional materials can be engineered by combining multiple chemical components, each conferring a well-defined function to the ensemble. Graphene is at the centre of an ever-growing research effort due to its combination of unique properties. Here we show that the large conformational change associated with the trans-cis photochemical isomerization of alkyl-substituted azobenzenes can be used to improve the efficiency of liquid-phase exfoliation of graphite, with the photochromic molecules acting as dispersion-stabilizing agents. We also demonstrate reversible photo-modulated current in two-terminal devices based on graphene-azobenzene composites. We assign this tuneable electrical characteristics to the intercalation of the azobenzene between adjacent graphene layers and the resulting increase in the interlayer distance on (photo)switching from the linear trans-form to the bulky cis-form of the photochromes. These findings pave the way to the development of new optically controlled memories for light-assisted programming and high-sensitive photosensors

EUROCARE-3: survival of cancer patients diagnosed 1990–94—results and commentary

EUROCARE-3 analysed the survival of 1 815584 adult cancer patients diagnosed from 1990 to 1994 in 22 European countries. The results are reported in tables, one per cancer site, coded according to the International Classification of Diseases (ICD)-9 classification. The main findings of the tables are summarised and commented on in this article. For most solid cancers, wide differences in survival between different European populations were found, as also reported by EUROCARE-1 and EUROCARE-2, despite a remarkable (10%) overall increase in cancer survival from 1985 to 1994. Survival was highest in northern Europe (Sweden, Norway, Finland and Iceland), and fairly good in central-southern Europe (France, Switzerland, Austria and Spain). Survival was particularly low in eastern Europe, low in Denmark and the UK, and fairly low in Portugal and Malta. The mix of tumour stage at diagnosis explains much of the survival differences for cancers of the digestive tract, female reproductive system, breast, thyroid, and also skin melanoma. For tumours of the urinary tract and prostate, the differences were explained mainly by differences in diagnostic criteria and procedures. The case mix by anatomic subsite largely explains differences in survival for head and neck cancers. For oesophagus, pancreas, liver and brain cancer, with poor prognoses, survival differences were limited. Tumours, for which highly effective treatments are available, such as testicular cancer, Hodgkin's lymphoma and some haematological malignancies, had fairly uniform survival across Europe. Survival for all tumours combined (an indicator of the overall cancer care performance of a nation's health system) was better in young than old patients, and better in women than men. The affluence of countries influenced overall cancer survival through the availability of adequate diagnostic and treatment procedures, and screening programmes. © 2003 European Society for Medical Oncology

Childhood cancer survival in Europe.

BACKGROUND: EUROCARE-3 collected data from 45 population-based cancer registries in 20 countries on 24 620 European children aged from 0 to 14 years diagnosed with malignancy in the period 1990-1994. METHODS: Five-year survival between countries was compared for all malignancies and for the major diagnostic categories, adjusting for age, and estimated average European survival weighting for differences in childhood populations. RESULTS: For all cancers combined, survival variation was large (45% in Estonia to 90% in Iceland), and was generally low (60-70%) in eastern Europe and high (> or =75%) in Switzerland, Germany and the Nordic countries (except Denmark). The Nordic countries had the highest survival for four of the seven major tumour types: nephroblastoma (92%), acute lymphoid leukaemia (85%), CNS tumours (73%) and acute non-lymphocytic leukaemia (62%). The eastern countries had lowest survival: 89% for Hodgkin's disease, 71% for nephroblastoma, 68% for acute lymphoid leukaemia, 61% for non-Hodgkin's lymphoma, 57% for central nervous system (CNS) tumours and 29% for acute non-lymphocytic leukaemia. CONCLUSIONS: The Nordic countries represent a survival gold standard to which other countries can aspire. Since most childhood cancers respond well to treatment, survival differences are attributable to differences in access (including referral and timely diagnosis) and use of modern treatments; however, the obstacles to access and application of standard treatments probably vary markedly with country

Hepatocellular carcinoma: Trends of incidence and survival in Europe and the United States at the end of the 20th century

OBJECTIVES: There is large geographic variation in incidence levels and time trends of hepatocellular carcinoma. We compared population-based liver cancer incidence and survival in European and U.S. populations in order to elucidate geographic differences and time trends for these variables. METHODS: Since comparisons based on cancer registry data are problematic because of variations in liver cancer definition and coding, we considered a subset of cases likely to be mainly hepatocellular carcinoma, suitable for international comparison. Incidence and 5-yr relative survival were calculated from cases diagnosed in five European regions (30,423 cases) and the United States (6,976 cases) in 1982-1994. RESULTS: Age-standardized incidence was highest in southern Europe (12/100,000 in men and 3/100,000 in women in 1992-94) and lowest in northern Europe, where incidence was similar to that of the United States (3/100,000 in men, <1/100,000 in women). Over the study period, incidence remained stable in the United States and most of Europe, except for a notable increase in southern Europe. Five-year relative survival was <10% in Europe, ranging from 8% (southern Europe) to 5% (eastern Europe), and 6% in the United States. Survival increased slightly with time, mainly in southern Europe and was unaffected by sex, but was better in younger patients. CONCLUSIONS: Increasing incidence in southern Europe is probably related to hepatitis B and C infection and increasing alcohol intake, while improving survival may be due to greater surveillance for cirrhosis. The survival gap between clinical and population-based series suggests management is better in centers of excellence. © 2007 by Am. Coll. of Gastroenterology