Theoretical study of the influence of the morphology in polymer-based devices functioning

It is well known that the morphology of polymer-based optoelectronic devices can influence their efficiency, since the ways that polymer chains pack inside the active layer can influence not only the charge transport but also the optic properties of the device. By using a mesoscopic model we carried out computer experiments to study the influence of the polymer morphology on the processes of charge injection, transport, recombination and collection by the electrodes opposite to those where the injection of bipolar charge carriers take place. Our results show that for polymer layers where the conjugated segments have perpendicular and random orientation relative to the electrodes surface, the competition between charge collection and charge recombination is affected when the average conjugation length of the polymer strands increase. This effect is more pronounced with the increase of the potential barrier at polymer/electrode interfaces that limit charge injection and increase charge collection. For these molecular arrangements the intra-molecular charge transport plays a major role in device performance, being this effect negligible when the polymer molecules have their axis parallel to the electrodes. Although the polymer morphology modelled in this work is far from real, we believe that our model can give some insights on the role of the microstructure on the functioning of polymer-based devices.European Community Fund (FEDER)Fundação para a Ciência e a Tecnologia (FCT) – Programa Operacional “Ciência , Tecnologia, Inovação” – POCTI/CTM/41574/2001, CONC-REEQ/443/EEI/2005 e SFRH/BD/22143/200

Quantum molecular dynamics simulations of conjugated polymers

The softness of conjugated polymers leads to strong coupling between polymer's electrons and lattice vibrations. Therefore, it is necessary to perform quantum molecular dynamics computer simulations in order to study their electronic and optical properties at molecular level. We have used self-consistent molecular dynamics calculations with interatomic forces evaluated from quantum mechanical calculations at the complete neglect of differential overlap level to discuss some of the issues relating to the electronic processes involved in polydiacetylene and poly(p-phenylene vinylene). Specifically addressed are the charge induced structural changes of the polymer chains and the intra-molecular charge mobility. The change in the chemical potential of individual polymer strands at zero temperature is also discussed. Our results suggest a geometrical distortion in the bond length distribution relative to the uncharged chains which is accompanied by changes in atomic charges at the distortion site. The charge carrier mobility is predicted to depend on the strength of the electric field, in accordance with experiments

Chemostratigraphy of the Pliensbachian, Puesto Araya Formation (Neuquén Basin, Argentina)

In a preliminary attempt to establish an isotope stratigraphy, strontium, carbon and oxygen isotope ratios were determined from marine biogenic carbonates of Pliensbachian age, in the context of scheme of local ammonite Zones correlatable to the European Standard Zonation. Two sections, rio Atuel and arroyo Serrucho, of the mainly siliciclastic Puesto Araya Formation, Neuquen Basin, south-western Mendoza, Argentina, were studied. Specimens of the bivalve genera Weyla Bhom and Gryphaea Lamarck were selected for the isotopic determinations because of their low-Mg calcite original mineralogy and widespread presence. Scanning electron microscopy, X-ray diffraction and X-ray fluorescence spectrometry techniques were used to control the good degree of preservation of most of the biogenic material, as evidenced by pristine fabrics, 100% calcite composition and Sr, Mn and Fe concentrations. Although strontium isotope ratios are slightly scattered, it is possible to compare them with those of the Early Jurassic seawater reference curve. Carbon isotope signals show two relative maxima, correlatable with those recorded for the upper part of the Ibex Zone and the middle part of the Margaritatus Zone in various European sections, indicating the possible global significance of these events. d18O values were found to be unreliable for isotope stratigraphy, as they are largely depleted in comparison to those of coeval unaltered marine carbonates

Épocas de floração de cultivares de oliveira em Castelo Branco, Elvas e Santarém

Comunicação apresentada no III Simpósio Nacional de Olivicultura que decorreu em Castelo Branco, de 29 a 31 de Outubro, na Escola Superior Agrária do Instituto Politécnico de Castelo Branco.A época de floração da oliveira está determinada pelas características genéticas inerentes a cada cultivar e é influenciada por factores climatéricos, variáveis de ano para ano. Esta influência do clima pode provocar importantes modificações anuais nas épocas de floração, aspecto fundamental para a calendarização das técnicas culturais do olival. Para além desta influência, a caracterização das épocas de floração é, também, importante para o estudo e conhecimento da adaptação de diferentes cultivares a uma região e para os programas de melhoramento genético, entre outros. Neste trabalho caracteriza-se a época de floração de cinco cultivares de oliveira, nas regiões de Castelo Branco, Elvas e Santarém, durante os anos de 2000, 2001 e 2002. Os resultados obtidos revelaram a existência de diferenças nas datas de floração e na duração de floração, entre cultivares e regiões, mantendo-se constante a ordem de entrada das cultivares em floração. As condições climatéricas prevalecentes no período de Janeiro a Maio, nomeadamente as temperaturas, condicionaram o calendário da floração, exercendo uma marcada influência no momento de início da floração e na duração do período de floração

Renal Allograft Rupture: A Clinicopathologic Review

Transplantation Proceedings Volume 32, Issue 8, December 2000, Pages 2597-2598 -------------------------------------------------------------------------------- doi:10.1016/S0041-1345(00)01801-7 | How to Cite or Link Using DOI Copyright © 2000 Elsevier Science Inc. All rights reserved. Cited By in Scopus (4) Permissions & Reprints Renal allograft rupture: a clinicopathologic review M Ramosa, , L Martinsa, L Diasa, A.C Henriquesa, J Soaresa, J Queirósa and A.M Sarmentoa aDepartments of Urology and Nefrology, Hospital Geral de Santo António, Oporto, Portugal Available online 19 December 2000. Article Outline Patients and methods Results Discussion References Renal allograft rupture (RAR) is a rare but very serious complication of renal transplantation, requiring emergency surgery. The most common cause is acute allograft rejection, but other causes such as renal vein thrombosis (RVT), acute tubular necrosis (ATN), renal biopsy, and lymphatic obstruction have been reported.[1] and [2] We reviewed our experience with the aim of identifying RAR predisposing conditions. Patients and methods In a consecutive series of 934 renal transplants performed between July 1983 and September 1999, 11 patients (1.2%) had RAR. In these cases we studied donor and recipient characteristics, preservation conditions, clinical signs and symptoms, treatment, and pathology findings. This group of patients was then compared with their paired cohort. Data analysis was computer-based. In the statistical analysis t test and Fisher’s exact test were used. Results All 11 kidneys that suffered RAR were from cadaver donors, nine male and two female. The mean age was 29.5 years with good terminal serum creatinine (mean 1.1 mg/dL). All organs were stored in Eurocollins solution and the mean cold ischemia time was 21 hours and 25 minutes (range, 10 hours to 29 hours and 20 minutes). Excluding one black patient, all recipients were Caucasian. Eight were female and 3 were male, with a mean age of 33.8 years. The mean HLA match was 1.7, and the mean peak panel reactive antibody (PRA) was 22% (range 0 to 93%) and current was 15% (range 0 to 67%). All patients had cyclosporine treatment, eight had delayed graft function requiring dialysis, and three underwent renal allograft biopsy. In two patients rupture occurred in the second allograft; the others were first transplants. The day of RAR was a mean of 5.3 (range 2 to 13). All patients had new onset of severe allograft pain, eight had a drop in daily hematocrit, and six had hypotension. The four patients with more precocious ruptures had sudden onset of bleeding through the drainage tube. Transplant nephrectomy was performed in 10 patients, and surgical conservative treatment with fibrin glue and collagen foam was performed in one. All patients survived RAR. Three had a second transplant and currently have functioning allografts. Pathology examination revealed RVT in three patients and some degree of rejection in the remaining eight. One patient had a rupture on the second day because of hyperacute rejection, and three had severe acute cellular rejection, but in four patients the dominant figure was ATN with minimal rejection. Excluding the patient with hyperacute rejection, the day of rupture was later for those with severe acute rejection, a mean of 9.6 days (range 6 to 13). In those with ATN, the day of RAR was a mean of 4.5 (range 3 to 6) and the patients with RVT had ruptures even sooner, on mean third day (range 2 to 4). Variables associated with RAR were: sex mismatch (P = .004), current PRA (P = .012), and a need for dialysis (P = .042). Age of the recipient, transplant number, cold ischemia time, total HLA match, and peak PRA were not associated with RAR. Discussion Higher current PRA and a need for dialysis are variables associated with rejection and ATN. Therefore they are expected to be related to rupture. The well-documented conditions that are associated with ATN and rejection3 must be the same, which in extreme conditions predispose to RAR. We find no explanation for the statistically significant association of sex mismatch and RAR, other than random error. Acute allograft rejection is the most frequent cause of graft rupture in the literature (60 to 80%),3 but ATN has received little note. In our series, ATN was responsible for 36% of the ruptures, as much as severe acute rejection. ATN alone can cause RAR,4 because of interstitial edema and rise in intrarenal pressure. But when associated with rejection, it seems that these two conditions can act synergistically to cause allograft rupture. Our data suggests that rupture occurs later when caused by rejection, rather than when RVT is responsible. To our knowledge this finding had never been reported in world literature. Perhaps the timing of RVT is related to technical problems, such as twisting and kinking of the vein or intima tear, although the thrombogenic effect of cyclosporine can also have a role in this process.5 All these patients were on cyclosporine therapy, which may explain the small number of RAR caused by rejection alone and the significant number of patients that had RVT (27%). It appears that cyclosporine therapy is changing the etiology of the graft rupture.6 References 1 T. Grochowiecki, J. Szmidt and K. Madej et al., Transplantation Proc 28 (1996), p. 3461. View Record in Scopus | Cited By in Scopus (2) 2 R.S. Lord, D.J. Effeney and J.M. Hayes et al., Ann Surg 177 (1973), p. 268. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (4) 3 G.J. Azar, A. Zarifian and G.D. Frentz et al., Clin Transplantation 10 (1996), p. 635. View Record in Scopus | Cited By in Scopus (12) 4 Y.H. Chan, K.M. Wong and K.C. Lee et al., Am J Kidney Dis 34 (1999), p. 355. Abstract | Article | PDF (86 K) 5 R.M. Jones, J.A. Murie and A. Ting et al., Clin Transplant 2 (1988), p. 122. 6 A.J. Richardson, R.M. Higgins and A.J. Jaskowski et al., Br J Surg 77 (1990), p. 558. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (19

Medium-modified average multiplicity and multiplicity fluctuations in jets

The energy evolution of average multiplicities and multiplicity fluctuations in jets produced in heavy-ion collisions is investigated from a toy QCD-inspired model. In this model, we use modified splitting functions accounting for medium-enhanced radiation of gluons by a fast parton which propagates through the quark gluon plasma. The leading contribution of the standard production of soft hadrons is enhanced by a factor $\sqrt{N_s}$ while next-to-leading order (NLO) corrections are suppressed by $1/\sqrt{N_s}$, where the parameter $N_s>1$ accounts for the induced-soft gluons in the medium. Our results for such global observables are cross-checked and compared with their limits in the vacuum.Comment: 8 pages and 4 figures. Version to be published in EPJ

Mesoscopic modelling of 2-CN-PPV/PPV polymer LED

Although optoelectronic devices made of polymers are very attractive ones (low cost, easy to make), problems related to charge transport, exciton quenching, among others, can be an obstacle for their performance. The use of heterojunctions made of two polymers can be a strategy for improving the efficiency of polymer light emitting diodes (PLEDs) at low bias. Here we present a theoretical study of the influence of bilayer structure in a PLED made of PPV and 2-CN-PPV, by adopting a mesoscopic approach. Our results show that the presence of the polymer/polymer interface improves charge injection and leads to a confinement of charges near it, which will increase the number recombination events in the middle of the device compared to the equivalent single-layer PLEDs.Fundação para a Ciência e a Tecnologia (FCT) Programa Operacional “Ciência , Tecnologia, Inovação” POCTI/CTM/41574/2001, CONC-REEQ/443/EEI/2001 e SFRH/BD/22143/200

Chemical composition of chestnut cultivars from Spain

Chestnut cultivation and production in Spain has employed grafted seedlings from selected local cultivars. Previously, we have characterised the Spanish cultivars by morphological and molecular markers. We are presenting in this paper the proximate analysis and mineral content for the main Spanish cultivars.Atotal of 131 sampleswere collected from47 cultivars in six important Spanish chestnut production regions; located in theNorth such as Asturias, Castilla-Leo´n (El Bierzo) and Galicia; in theCentral such as Extremadura and in the South such as Andalucı´a; as well as theCanary Islands, the southermost part of Spain near to North Africa. High variability in chemical composition between cultivars and regions corresponded to the high genetic variability between cultivars. Correlations with environmental parameters were low, indicating that differences found between regions were probably reflecting the differences between cultivars. In Central and Southern Spain, some cultivars presented lowest moisture content due to the low summer rainfall in these regions. Differences in starch and total sugar contents were high and were negatively correlated with each other. Therewas no negative correlation between nut size and total sugar content.Lowest values of fibre content and ease of digestibilitywere found in cultivars fromGalicia and Extremadura. No significant differences in Fe, Zn and Cu were found although Zn content is twice the value reported for European chestnuts. This work would be a valuable reference to chestnut quality for the food processing industry, nutritionists, breeders and growers alike

Familial hypercholesterolemia: Molecular characterization of possible cases from the Azores Islands (Portugal)

Familial hypercholesterolemia (FH) is an autosomal dominant disorder of the cholesterol metabolism, which constitutes a risk factor for coronary arterial disease (CAD). In the Azores Islands (Portugal), where mortality from CAD doubles its rate comparatively to the rest of the country and where a high frequency of dyslipidemia has been reported, the prevalence and distribution of FH remain unknown. The molecular characterization of a group of 33 possible cases of FH of Azorean background was undertaken in this study. A DNA array was initially used to search mutations in the LDLR, APOB and PCSK9 loci in 10 unrelated possible cases of FH. No mutations were detected in the array; after sequencing the full LDLR gene, 18 variants were identified, corresponding to two missense (c.806G > A; c.1171G > A) and sixteen synonymous alterations. Six of the synonymous variants which are consistently described in the literature as associated with altered cholesterol levels were used to build haplotypes. The most frequent haplotype corresponded to TTCGCC (45%), a "risk" haplotype, formed exclusively by alleles that were reported to increase cholesterol levels. Some of the variants detected in the full sequencing of the LDLR gene fell within the ligand-binding domain of this gene, defined by exons 2 to 6. To add information as to the role of such variants, these exons were sequenced in the remaining 23 possible FH cases. Two missense alterations (c.185C > T; c.806G > A) were found in this subset of possible FH cases. The missense alteration c.185C > T, identified in one individual, is novel for the Portuguese population. In silico analysis was not conclusive for this alteration, whose role will have to be further investigated. This study represents the first approach to the establishment of the mutational profile of FH in the Azores Islands.This work was supported by the project entitled “High prevalence pathologies in the Azores: genetic and biochemical markers” with reference (M2.1.2/I/026/2008) funded by SRCTE. M. R. receives a PhD fellowship (M3.1.2/F/006/2011) from Fundo Regional para a Ciência. T.C. receives a post-doctoral fellowships from Fundação para a Ciência e a Tecnologia (SFRH/BPD/38659/ 2007) and N. K. (M3.1.7/F/002/2008) and A. R. (M3.1.7/F/031/2011) both receives post-doctoral fellowships from Fundo Regional para a Ciência