1,650 research outputs found
Recursive calculation of time to ruin distributions
In this paper we present a different approach on Dickson and Waters [Astin Bulletin 21 (1991) 199] and De Vylder and Goovaerts [Insurance: Mathematics and Economics 7 (1988) 1] methods to approximate time to ruin probabilities. By means of Markov chain application we focus on the direct calculation of the distribution of time to ruin, and we find that the above recursions appear to be less efficient, although giving the same approximation figures. We show some graphs of the time to ruin distribution for some examples, comparing the different shapes of the densities for different values of the initial surplus. Furthermore, we consider the presence of an upper absorbing barrier and apply the proposed recursion to find ruin probabilities in this case..info:eu-repo/semantics/publishedVersio
Early pseudoprogression following chemoradiotherapy in glioblastoma patients: the value of RANO evaluation
Early Pseudo-progression Following Chemoradiotherapy in Glioblastoma Patients: The Value of RANO EvaluationThe aim of this study was to determine the frequency of pseudoprogression in a cohort of glioblastoma (GBM) patients following radiotherapy/temozolomide (RT/TMZ) by comparing Macdonald criterial to Response Assessment in Neuro-Oncology (RANO) criteria. The impact on prognosis and survival analysis was also studied. Materials and Methods. All patients receiving RT/TMZ for newly diagnosed GBM from January 2005 to December 2009 were retrospectively evaluated, and demographic, clinical, radiographic, treatment, and survival data were reviewed. Updated RANO criteria were used for the evaluation of the pre-RT and post-RT MRI and compared to classic Macdonald criteria. Survival data was evaluated using the Kaplan-Meier and log-rank analysis. Results and Discussion. 70 patients were available for full radiological response assessment. Early progression was confirmed in 42 patients (60%) according to Macdonald criteria and 15 patients (21%) according to RANO criteria. Pseudoprogression was identified in 10 (23.8%) or 2 (13.3%) patients in Macdonald and RANO groups, respectively. Cumulative survival of pseudoprogression group was higher than that of true progression group and not statistically different from the non-progressive disease group. Conclusion. In this cohort, the frequency of pseudoprogression varied between 13% and 24%, being overdiagnosed by older Macdonald criteria, which emphasizes the importance of RANO criteria and new radiological biomarkers for correct response evaluation.The authors acknowledge Francisco Soares, MD, for statistical support
Adipose tissue derived stem cells secretome: soluble factors and their roles in regenerative medicine
Stem cells have been long looked at as possible therapeutic vehicles for different health related problems. Among the different
existing stem cell populations, Adipose derived Stem Cells (ASCs) have been gathering attention in the last 10 years. When compared to
other stem cells populations and sources, ASCs can be easily isolated while providing higher yields upon the processing of adipose tissue.
Similar to other stem cell populations, it was initially thought that the main potential of ASCs for regenerative medicine approaches was
intimately related to their differentiation capability. Although this is true, there has been an increasing body of literature describing the
trophic effects of ASCs on the protection, survival and differentiation of a variety of endogenous cells/tissues. Moreover, they have also
shown to possess an immunomodulatory character. This effect is closely related to the ASCsā secretome and the soluble factors found
within it. Molecules such as hepatocyte growth factor (HGF), granulocyte and macrophage colony stimulating factors, interleukins (ILs)
6, 7, 8 and 11, tumor necrosis factor-Ī± (TNF-Ī±), vascular endothelial growth factor (VEGF), brain derived neurotrophic factor (BDNF),
nerve growth factor (NGF), adipokines and others have been identified within the ASCsā secretome. Due to its importance regarding future
applications for the field of regenerative medicine, we aim, in the present review, to make a comprehensive analysis of the literature
relating to the ASCsā secretome and its relevance to the immune and central nervous system, vascularization and cardiac regeneration.
The concluding section will highlight some of the major challenges that remain before ASCs can be used for future clinical applications
AvaliaĆ§Ć£o de matriz cimentĆcia contendo cinzas volantes frente Ć aĆ§Ć£o combinada da carbonataĆ§Ć£o e dos iƵes cloreto
As cinzas volantes (CV) tĆŖm sido utilizadas para tornar a matriz cimentĆcia mais resistente Ć penetraĆ§Ć£o de Cl- uma vez que tornam a estrutura porosa mais densa. Por outro lado, sabe-se que o Ca(OH) existente na matriz Ć© parcialmente consumido pelas reaƧƵes pozolĆ¢nicas, facilitando o avanƧo da carbonataĆ§Ć£o. Considerando a aĆ§Ć£o conjunta destes agentes, especula-se sobre o comportamento da matriz. Foram moldados provetes com 40% de CV (substituiĆ§Ć£o). ApĆ³s 90 dias de cura os provetes foram submetidos a 12 ciclos de imersĆ£o (3,5% NaCl)/secagem (4% CO2) e 12 ciclos de referĆŖncia,168 dias. Os resultados indicam que os provetes submetidos Ć aĆ§Ć£o combinada apresentam uma profundidade de carbonataĆ§Ć£o inferior em relaĆ§Ć£o Ć aĆ§Ć£o exclusiva do CO2. Ao contrĆ”rio, apresentam um perfil de Cl- com teores superiores quando comparados Ć aĆ§Ć£o exclusiva dos Cl-.
EvoluĆ§Ć£o da frente de carbonataĆ§Ć£o em argamassas contendo cinzas volantes tendo em conta a presenƧa de iƵes cloreto
Vol.1A incorporaĆ§Ć£o de cinzas volantes (CV) em matrizes cimentĆcias tem sido frequentemente utilizada com objetivo de tornar a matriz mais resistente Ć aĆ§Ć£o dos cloretos. Por outro lado, sabe-se que o Ca(OH) existente na matriz Ć© parcialmente consumido pelas reaƧƵes pozolĆ¢nicas, o que facilita o avanƧo da frente de carbonataĆ§Ć£o. Tendo em conta que a aĆ§Ć£o conjunta entre a carbonataĆ§Ć£o e a penetraĆ§Ć£o de cloretos Ć© uma realidade ainda pouco conhecida, especula-se sobre o comportamento da matriz face a esta aĆ§Ć£o combinada. Assim, este trabalho investiga a influĆŖncia da presenƧa de cloretos sobre a frente de carbonataĆ§Ć£o em argamassas contendo CV. Foram moldados provetes com 0% e 40% de substituiĆ§Ć£o de cimento CEM I 42,5R por CV e relaĆ§Ć£o Ć”gua/ligante de 0,56 e 0,52, respetivamente. ApĆ³s 90 dias de cura os provetes foram submetidos a ciclos de imersĆ£o/secagem por 56 dias. Metade dos provetes foi submetida ao seguinte ciclo: 2 dias em soluĆ§Ć£o contendo NaCl (concentraĆ§Ć£o igual a 3,5%); 12 dias em cĆ¢mara de carbonataĆ§Ć£o (4% de teor de CO
2). A outra metade esteve: 2 dias em Ć”gua destilada; 12 dias em cĆ¢mara de carbonataĆ§Ć£o. Em seguida, a evoluĆ§Ć£o da frente de carbonataĆ§Ć£o foi avaliada. Os resultados indicam que a presenƧa de cloretos exerce influĆŖncia sobre a carbonataĆ§Ć£o. Os provetes submetidos Ć aĆ§Ć£o exclusiva do CO2 apresentaram uma profundidade de carbonataĆ§Ć£o superior aquela apresentada pelos provetes submetidos Ć aĆ§Ć£o combinada. Este fato pode estar relacionado com alteraƧƵes em propriedades da matriz que podem conduzir a um maior refinamento dos poros e com a presenƧa do sal que pode conduzir ao preenchimento parcial dos poros e ao aumento no teor de humidade
InfluĆŖncia da carbonataĆ§Ć£o no transporte de cloretos em argamassas submetidas Ć aĆ§Ć£o combinada destes dois agentes
Vol.2Para assegurar a sustentabilidade das estruturas de betĆ£o armado Ć© fundamental garantir a sua durabilidade. Neste contexto, conhecer o modo como estas estruturas reagem Ć aĆ§Ć£o dos agentes agressores assume grande importĆ¢ncia. A corrosĆ£o dos varƵes de aƧo Ć© o problema que mais afeta a durabilidade sendo que, a carbonataĆ§Ć£o e o ingresso de cloretos sĆ£o as duas principais causas da corrosĆ£o. Apesar da aĆ§Ć£o combinada destes agentes ser uma realidade, ainda nĆ£o hĆ” consenso acerca do efeito da carbonataĆ§Ć£o sobre a penetraĆ§Ć£o de cloretos no betĆ£o. Este trabalho analisa a influĆŖncia da carbonataĆ§Ć£o sobre a penetraĆ§Ć£o de cloretos atravĆ©s de ensaios acelerados. Para isso, foram moldados provetes em argamassa utilizando cimento CEM I 42,5R e relaĆ§Ć£o Ć”gua/cimento 0,56. ApĆ³s 90 dias de cura os provetes foram submetidos a ciclos de imersĆ£o/secagem por 56 e 168 dias. Metade dos provetes foram submetidos ao seguinte ciclo: 2 dias em soluĆ§Ć£o contendo NaCl (3,5%); 12 dias em cĆ¢mara de carbonataĆ§Ć£o (4% de CO
). A outra metade esteve: 2 dias na mesma soluĆ§Ć£o; 12 dias em ambiente de laboratĆ³rio. Terminado o perĆodo de ensaio, a penetraĆ§Ć£o dos agentes agressores foi avaliada atravĆ©s do perfil de cloretos total e da profundidade de carbonataĆ§Ć£o. Ensaios complementares tambĆ©m foram realizados. Os resultados obtidos mostram que a carbonataĆ§Ć£o tem uma influĆŖncia direta sobre a penetraĆ§Ć£o de cloretos. Amostras nĆ£o carbonatadas apresentaram um perfil com teores de cloretos mais elevados do que as amostras carbonatadas. Este fato pode estar relacionado com o refinamento dos poros causado pela carbonataĆ§Ć£o e observado no ensaio de absorĆ§Ć£o capilar
The effect of insulin-loaded chitosan particle-aggregated scaffolds in chondrogenic differentiation
Osteochondral defect repair requires a tissue engineering approach that aims at mimicking the physiological
properties and structure of two different tissues (cartilage and bone) using a scaffoldācell construct. One ideal
approach would be to engineer in vitro a hybrid material using a single-cell source. For that purpose, the scaffold
should be able to provide the adequate biochemical cues to promote the selective but simultaneous differentiation
of both tissues. In this work, attention was paid primarily to the chondrogenic differentiation by focusing
on the development of polymeric systems that provide biomolecules release to induce chondrogenic differentiation.
For that, different formulations of insulin-loaded chitosan particleāaggregated scaffolds were developed
as a potential model system for cartilage and osteochondral tissue engineering applications using insulin as a
potent bioactive substance known to induce chondrogenic differentiation. The insulin encapsulation efficiency
was shown to be high with values of 70.37!0.8%, 84.26!1.76%, and 87.23!1.58% for loadings of 0.05%, 0.5%,
and 5%, respectively. The in vitro release profiles were assessed in physiological conditions mimicking the cell
culture procedures and quantified by Micro-BCA! protein assay. Different release profiles were obtained that
showed to be dependent on the initial insulin-loading percentage. Further, the effect on prechondrogenic
ATDC5 cells was investigated for periods up to 4 weeks by studying the influence of these release systems on
cell morphology, DNA and glycosaminoglycan content, histology, and gene expression of collagen types I and II,
Sox-9, and aggrecan assessed by real-time polymerase chain reaction. When compared with control conditions
(unloaded scaffolds cultured with the standard chondrogenic-inducing medium), insulin-loaded scaffolds upregulated
the Sox-9 and aggrecan expression after 4 weeks of culture. From the overall results, it is reasonable to
conclude that the developed loaded scaffolds when seeded with ATDC5 can provide biochemical cues for
chondrogenic differentiation. Among the tested formulations, the higher insulin-loaded system (5%) was the
most effective in promoting chondrogenic differentiation.The authors would like to acknowledge the Portuguese Foundation for Science and Technology for the Ph. D. Grant to Patricia B. Malafaya (SFRH/BD/11155/2002). This work was partially supported and carried out under the scope of the European STREP Project HIPPOCRATES (NMP3-CT-2003-505758) and European NoE EXPERTISSUES (NMP3CT-2004-500283). The authors also like to acknowledge the Life and Health Sciences Research Institute (ICVS), University of Minho, for the use of their facilities, namely, to Luis Martins for histological sections slicing and H&E stain processing
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