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  • Name

    Andreia Sofia Teixeira
  • Cluster

    Computer Science
  • Role

    Researcher
  • Since

    16th January 2018
Publications

2017

Sophistication vs Logical Depth

Authors
Antunes, L; Bauwens, B; Souto, A; Teixeira, A;

Publication
THEORY OF COMPUTING SYSTEMS

Abstract
Sophistication and logical depth are two measures that express how complicated the structure in a string is. Sophistication is defined as the minimal complexity of a computable function that defines a two-part description for the string that is shortest within some precision; the second can be defined as the minimal computation time of a program that is shortest within some precision. We show that the Busy Beaver function of the sophistication of a string exceeds its logical depth with logarithmically bigger precision, and that logical depth exceeds the Busy Beaver function of sophistication with logarithmically bigger precision. We also show that sophistication is unstable in its precision: constant variations can change its value by a linear term in the length of the string.

2016

Distinguishing Two Probability Ensembles with One Sample from each Ensemble

Authors
Antunes, L; Buhrman, H; Matos, A; Souto, A; Teixeira, A;

Publication
THEORY OF COMPUTING SYSTEMS

Abstract
We introduced a new method for distinguishing two probability ensembles called one from each method, in which the distinguisher receives as input two samples, one from each ensemble. We compare this new method with multi-sample from the same method already exiting in the literature and prove that there are ensembles distinguishable by the new method, but indistinguishable by the multi-sample from the same method. To evaluate the power of the proposed method we also show that if non-uniform distinguishers (probabilistic circuits) are used, the one from each method is not more powerful than the classical one, in the sense that does not distinguish more probability ensembles. Moreover we obtain that there are classes of ensembles, such that any two members of the class are easily distinguishable (a definition introduced in this paper) using one sample from each ensemble; there are pairs of ensembles in the same class that are indistinguishable by multi-sample from the same method.

2016

Peripheral vasculopathy in Raynaud phenomenon: Vascular disease biomarkers

Authors
Silva, I; Teixeira, A; Oliveira, J; Almeida, R; Vasconcelos, C;

Publication
Angiologia e Cirurgia Vascular

Abstract
Background Introduction: Raynaud's phenomenon (RP) is a well-defined clinical syndrome. Systemic sclerosis (SSc) is the most frequent associated disease to RP (96%). The aim of this study was to assess the differences between primary RP (PRP) and secondary RP (SRP) regarding macrovascular disease parameters, endothelial dysfunction and angiogenesis biomarkers. Materials and methods Flow-mediated dilatation (FMD), endothelin-1 (ET-1), asymmetric dimethylarginine (ADMA) vascular endothelial growth factor (VEGF), endoglin and endostatin were analyzed in a cohort study of 32 PRP patients and 77 SRP all with SSc. 38 of the SRP SSc-associated patients had severe digital ulcer (DU). Results Patients with PRP had significantly longer history of RP compared to SRP SSc-sssociated patients (p = 0.028). FMD was significantly lower in SRP patients 10.85 ± 11.0% (p < 0.001), more evidenced in SRP SSc-associated DU patients 5.34 ± 7.49 (p < 0.001). ET-1 plasma levels were significantly increased in both PRP 7.53 (0.16-11.73) and SRP patients 11.85 (7.42-17.23) (p < 0.001). Significant increased serum levels of ADMA 0.52 (0.45-0.63) µmol/L (p < 0.001) and endoglin 3.01 (1.46-7.02) mg/ml (p < 0.001) were found in the SRP SSc-associated group with DU. VEGF was significantly decreased in the DU group 245.06 (158.68-347.33) pg/ml compared to PRP 438.50 (269.26-854.00) pg/ml and SRP naïve-DU patients 290 (166.71-361.78) pg/ml patients (p < 0.001). No significant differences were found between groups regarding endostatin (p = 0.118). Comparing PRP and SRP SSc-associated patients without DU no statistically significant difference regarding FMD, ET-1, ADMA, VEGF, plasma levels were observed. Conclusion Overproduction of ET-1 and VEGF is present in PRP patients. Macrovascular disease and an impaired response to shear stress are more characteristic of SRP with a grater expression in patients with peripheral ischemic lesions. © 2016 Sociedade Portuguesa de Angiologia e Cirurgia Vascular.

2015

Portuguese Family Physicians' Awareness of Diagnostic and Laboratory Test Costs: A Cross-Sectional Study

Authors
Sa, L; Costa Santos, C; Teixeira, A; Couto, L; Costa Pereira, A; Hespanhol, A; Santos, P; Martins, C;

Publication
PLOS ONE

Abstract
Background Physicians' ability to make cost-effective decisions has been shown to be affected by their knowledge of health care costs. This study assessed whether Portuguese family physicians are aware of the costs of the most frequently prescribed diagnostic and laboratory tests. Methods A cross-sectional study was conducted in a representative sample of Portuguese family physicians, using computer-assisted telephone interviews for data collection. A Likert scale was used to assess physician's level of agreement with four statements about health care costs. Family physicians were also asked to estimate the costs of diagnostic and laboratory tests. Each physician's cost estimate was compared with the true cost and the absolute error was calculated. Results One-quarter (24%; 95% confidence interval: 23%-25%) of all cost estimates were accurate to within 25% of the true cost, with 55% (95% IC: 53-56) overestimating and 21% (95% IC: 20-22) underestimating the true actual cost. The majority (76%) of family physicians thought they did not have or were uncertain as to whether they had adequate knowledge of diagnostic and laboratory test costs, and only 7% reported receiving adequate education. The majority of the family physicians (82%) said that they had adequate access to information about the diagnostic and laboratory test costs. Thirty-three percent thought that costs did not influence their decision to order tests, while 27% were uncertain. Conclusions Portuguese family physicians have limited awareness of diagnostic and laboratory test costs, and our results demonstrate a need for improved education in this area. Further research should focus on identifying whether interventions in cost knowledge actually change ordering behavior, in identifying optimal methods to disseminate cost information, and on improving the cost-effectiveness of care.

2015

Digital ulcers in systemic sclerosis: role of flow-mediated dilatation and capillaroscopy as risk assessment tools

Authors
Silva, I; Loureiro, T; Teixeira, A; Almeida, I; Mansilha, A; Vasconcelos, C; Almeida, R;

Publication
EUROPEAN JOURNAL OF DERMATOLOGY

Abstract
Aim: The aim of this study was to evaluate macrovascular endothelial dysfunction and microvascular damage as clinical markers of peripheral microangiopathy in patients with Raynaud's phenomenon (RP). Patients and methods: Seventy-seven secondary RP with systemic sclerosis, 32 primary RP and 34 healthy controls were included in our study. Secondary RP patients were divided into two subgroups: 39 with digital ulcers (DU) and 38 without digital ulcers (non-DU). Results: Patients with DU had significantly lower flow-mediated dilatation values (5.34 +/- 7.49%) compared to non-DU patients (16.21 +/- 11.31%), primary RP (17.96 +/- 12.78%) and controls (20.17 +/- 8.86%), p<0.001, favouring macrovascular endothelium dysfunction. Regarding microvascular damage, the DU group had a predominately capillaroscopic late pattern (71.1%) whereas non-DU patients had an active pattern (56.4%). The microangiopathy evolution score was significantly higher in the DU group compared to the non-DU group (4.79 +/- 1.82 vs. 1.79 +/- 1.56, p<0.001). Flow-mediated dilation was significantly lower in late pattern (6.13 +/- 7.09%) compared to active (12.58 +/- 10.66%) and early patterns (17.72 +/- 14.90%), p = 0.016 and p = 0.044 respectively. Conclusions: Low flow-mediated dilatation and microvascular damage in capillaroscopy are early clinical markers of DU risk in RP patients.