626 research outputs found
Statistical stability of equilibrium states for interval maps
We consider families of multimodal interval maps with polynomial growth of
the derivative along the critical orbits. For these maps Bruin and Todd have
shown the existence and uniqueness of equilibrium states for the potential
, for close to 1. We show that these
equilibrium states vary continuously in the weak topology within such
families. Moreover, in the case , when the equilibrium states are
absolutely continuous with respect to Lebesgue, we show that the densities vary
continuously within these families.Comment: More details given and the appendices now incorporated into the rest
of the pape
Da angiogénese à terapêutica oncológica antiangiogénica
Os avanços ocorridos na área da biologia molecular possibilitam uma melhor compreensão dos mecanismos de carcinogénese. Nestes, destaca-se a angiogénese como o processo através do qual as células tumorais estimulam a formação dos novos vasos sanguíneos necessários para o fornecimento dos nutrientes essenciais para seu crescimento acelerado. A angiogénese tumoral é regulada pela produção de estimuladores da angiogénese, incluindo membros da família dos factores de crescimento do endotélio vascular (VEGF) e dos factores de crescimento dos fibroblastos (FGF).
Os tumores podem activar inibidores angiogénicos como a angiostatina e a endostatina, que podem modular a angiogénese, tanto no local do tumor como em locais metastáticos. O uso de inibidores angiogénicos como drogas antineoplásicas está actualmente sob intensa investigação. Tais agentes podem ter uma toxicidade reduzida e serem menos susceptíveis de gerar resistência do que as drogas citotóxicas convencionais. Os ensaios clínicos estão em andamento para desenvolver estratégias de tratamento ideal com os agentes antiangiogénicos
The compound Poisson limit ruling periodic extreme behaviour of non-uniformly hyperbolic dynamics
We prove that the distributional limit of the normalised number of returns to
small neighbourhoods of periodic points of non-uniformly hyperbolic dynamical
systems is compound Poisson. The returns to small balls around a fixed point in
the phase space correspond to the occurrence of rare events, or exceedances of
high thresholds, so that there is a connection between the laws of Return Times
Statistics and Extreme Value Laws. The fact that the fixed point in the phase
space is a repelling periodic point implies that there is a tendency for the
exceedances to appear in clusters whose average sizes is given by the Extremal
Index, which depends on the expansion of the system at the periodic point.
We recall that for generic points, the exceedances, in the limit, are
singular and occur at Poisson times. However, around periodic points, the
picture is different: the respective point processes of exceedances converge to
a compound Poisson process, so instead of single exceedances, we have entire
clusters of exceedances occurring at Poisson times with a geometric
distribution ruling its multiplicity.
The systems to which our results apply include: general piecewise expanding
maps of the interval (Rychlik maps), maps with indifferent fixed points
(Manneville-Pomeau maps) and Benedicks-Carleson quadratic maps.Comment: To appear in Communications in Mathematical Physic
Chemical Differentiation of Sugarcane Cultivars Based on Volatile Profile and Chemometric Analysis
Sugarcane (SC) is a perennial grass widely cultivated in tropical and subtropical regions. However, its cultivation in
Europe is residual, where Madeira Island, Portugal, is the only region where SC continues to be extensively cultivated. For the first
time, the volatile profiles of regional cultivars were established by solid-phase microextraction combined with gas chromatography−
mass spectrometry. Different volatile profiles for each cultivar were recognized, identifying 260 volatile organic compounds
belonging to 15 chemical classes, such as aldehydes, alcohols, ketones, hydrocarbons, esters, and terpenes. Chemometric analysis
procedure, namely, one-way ANOVA with Tukey’s test, principal component analysis, partial least-square analysis, linear
discriminant analysis, and hierarchical clustering analysis, allowed the differentiation between all regional cultivars. This study
represents an important contribution for the maintenance of biodiversity and subsistence of the SC industry in Europe. Furthermore,
it is also a valuable contribution to establish the typicality of traditional SC-based products, such as SC honey.info:eu-repo/semantics/publishedVersio
A Predictive Strategy Based on Volatile Profile and Chemometric Analysis for Traceability and Authenticity of Sugarcane Honey on the Global Market
Sugarcane honey (SCH) is a syrup produced on Madeira Island and recognized by its
unique aroma, a complex attribute of quality with an important influence on the final consumer’s
acceptance of the product, and determined by a complex mixture of a large number of volatile organic
compounds (VOCs) generated during its traditional making process and storage. Therefore, the
purpose of this study was to establish the volatile profile of genuine SCH produced by a regional
certified producer for seven years and compare it with syrups from non-certified regional producers
and with producers from different geographical regions (Spain, Egypt, Brazil and Australia), as
a powerful strategy to define the volatomic fingerprint of SCH. Different volatile profiles were
recognized for all samples, with 166 VOCs being identified belonging to different chemical classes,
including furans, ketones, carboxylic acids, aldehydes and alcohols. Chemometric analysis allowed
(i) the differentiation between all syrups, being more pronounced between SCH and other syrups;
and (ii) the identification of 32 VOCs as potential markers for the traceability and authenticity of
SCH on the global market.info:eu-repo/semantics/publishedVersio
Effect of processing and storage on the volatile profile of sugarcane honey: A four-year study
Sugarcane honey (SCH) is a syrup from Madeira Island recognized by its unique and excellent aroma, associated
to volatile organic compounds (VOCs) generated during the well-defined five stages of its traditional making
process. The establishment of volatile profile throughout all SCH-making stages during four years, allowed the
evaluation of the influence of each stage in the typical characterisitcs of SCH. One hundred eighthy seven VOCs
were identified, being associated to several origins and formation pathways. VOCs formed during stage 1 and 2
were originate from raw material, and its oxidation (i.e. enzymatic browning) and thermal degradation (i.e. lipid
oxidation, Maillard reactions, Strecker degradation). In stage 3 and 4, the caramelization and melanoidin
degradation also occurred, while in stage 5, the thermal degradation continues, followed by microbial activity.
Chemometric analysis allowed to identify 35 VOCs as potential markers for processing control by the producers
and as guarantee of the typicality and authenticity of SCH. Based on the obtained results, we propose for the first
time an innovative schematic diagram explaining the potential reactions and pathways for VOCs formation
during the different steps of the SCH production.info:eu-repo/semantics/publishedVersio
A 26-Year Experience in Chorionic Villus Sampling Prenatal Genetic Diagnosis
Abstract: This report describes the trends of chorionic villus sampling (CVS) referred for prenatal genetic diagnosis in the past two and a half decades in a Portuguese Center. Our cohort of 491 CVS was mostly performed by the transcervical method at the 12th gestational week. Data collected within the framework of this study relate to the following: sampling method, referral reason versus abnormality and incidence of procedure-related pregnancy loss, that declined to about 0.5% over the last 15 years. The year 2000 represented a change in referral reasons for chorionic tissue collection, shifting from almost exclusively for cytogenetic testing to an increasing number of molecular tests for monogenic disorders. Herein, success rates as well as cytogenetic and/or molecular DNA results are presented. These latter include not only tests for several monogenic disorders, but also aneuploidy and maternal cell contamination screening. This retrospective analysis reiterates that CVS is a safe and reliable first trimester technique for prenatal diagnosis in high genetic risk pregnancies
Molecular diagnosis and typing of Trypanosoma cruzi populations and lineages in cerebral Chagas disease in a patient with AIDS
Trypanosoma cruzi DNA was amplified from an intracranial biopsy and peripheral blood of an HIV patient with encephalitis; this episode was indicative of AIDS and congenital Chagas disease. The analysis of a microsatellite locus revealed a multiclonal parasite population at the brain lesion with a more complex minicircle signature than that profiled in blood using restriction fragment length polymorphism (RFLP)-PCR and low stringency single primer (LSSP) PCR. Interestingly, different sublineages of T. cruzi II were detected in blood and brain by means of spliced-leader and 24s ribosomal-DNA amplifications. Quantitative-competitive PCR monitored the decrease of parasitic load during treatment and secondary prophylaxis with benznidazole. The synergy between parasiticidal plus antiretroviral treatments probably allowed the patient a longer survival than usually achieved in similar episodes. This is the first case report demonstrating a differential distribution of natural parasite populations and sublineages in Chagas disease reactivation, showing the proliferation of cerebral variants not detectable in peripheral blood.Fil: Burgos, Juan Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Bergher, Sandra B.. Gobierno de la Ciudad de Buenos Aires. Hospital "Ignacio Pirovano"; ArgentinaFil: Freitas, Jorge M.. Universidade Federal de Minas Gerais; BrasilFil: Bisio, Margarita María Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Altcheh, Jaime Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de la Ciudad de Buenos Aires. Hospital General de Niños "Ricardo Gutiérrez"; ArgentinaFil: Teijeiro, Ricardo. Gobierno de la Ciudad de Buenos Aires. Hospital "Ignacio Pirovano"; ArgentinaFil: Begher, Sandra B.. Gobierno de la Ciudad de Buenos Aires. Hospital "Ignacio Pirovano"; ArgentinaFil: Freilij, Hector León. Gobierno de la Ciudad de Buenos Aires. Hospital General de Niños "Ricardo Gutiérrez"; ArgentinaFil: Deccarlini, Florencia. Gobierno de la Ciudad de Buenos Aires. Hospital "Ignacio Pirovano"; ArgentinaFil: Levalle, Jorge. Gobierno de la Ciudad de Buenos Aires. Hospital "Ignacio Pirovano"; ArgentinaFil: Lopez Alcoba, Horacio. Gobierno de la Ciudad de Buenos Aires. Hospital "Ignacio Pirovano"; ArgentinaFil: Burgos, Juan Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Fisiología, Biología Molecular y Celular; ArgentinaFil: Levin, Mariano Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Duffy, Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Macedo, Andrea M.. Universidade Federal de Minas Gerais; BrasilFil: Schijman, Alejandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentin
Chemical characterization and antioxidant activities of oligomeric and polymeric procyanidin fractions from grape seeds
Two procyanidin fractions, namely oligomers and polymers isolated from grape seed methanolic extract were characterized. Phenolic
composition and procyanidin purity of these fractions were determined by normal-phase and reverse-phase HPLC, thioacidolysis-HPLC,
ESI-MS analyses, formaldehyde–HCl precipitation and elemental analysis. Antioxidant activities of these fractions and other wellknown
antioxidants were measured using xanthine–xanthine oxidase system for generating superoxide radical ({O
2 }), the DPPH
(1,1-diphenyl-2-picrylhydrazyl) radical method and the Fenton system for generating hydroxyl radical (HO ). The results showed that
both oligomeric and polymeric procyanidin fractions were highly pure, with the degree of polymerization ranging from 2 to 17–18
and 12 to 32–37, respectively. On the basis of molar concentration, polymeric procyanidins appeared the highest antioxidant activities,
followed by oligomeric procyanidins, whereas catechins presented a lower antioxidant activity than its oligomers and polymers. These
results indicate that the antioxidant activities of grape seed procyanidins are positively related to their degree of polymerization. Moreover,
grape seed procyanidins presented higher antioxidant activities than other well-known antioxidants such as vitamin C, suggesting
that grape seed procyanidins might be of interest to be used as alternative antioxidant
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