A study of the double pendulum using polynomial optimization.

In dynamical systems governed by differential equations, a guarantee that trajectories emanating from a given set of initial conditions do not enter another given set can be obtained by constructing a barrier function that satisfies certain inequalities on the phase space. Often, these inequalities amount to nonnegativity of polynomials and can be enforced using sum-of-squares conditions, in which case barrier functions can be constructed computationally using convex optimization over polynomials. To study how well such computations can characterize sets of initial conditions in a chaotic system, we use the undamped double pendulum as an example and ask which stationary initial positions do not lead to flipping of the pendulum within a chosen time window. Computations give semialgebraic sets that are close inner approximations to the fractal set of all such initial positions.

Written Health Education Materials for Women with Gestational Diabetes Mellitus - Evaluation of Usefulness and Patients' Satisfaction.

BACKGROUND: Written health educational materials are an integral part of the treatment process. Because of the constantly increasing gestational diabetes mellitus (GDM) global rate, pregnant women require accessible, easy-to-understand and evidence-based medical information about this pregnancy complication. AIM: To adapt and elaborate printed educational materials on GDM and to evaluate the usefulness of the produced training materials and pregnant women's satisfaction. MATERIALS AND METHODS: The present study implemented a methodological approach covering three phases: (1) systematic literature review; (2) compilation of printed educational materials for pregnant women with GDM; (3) evaluation of the usefulness and satisfaction with the produced educational materials through a focus group consisting of pregnant women. A seven-item self-administered feedback questionnaire was adopted for evaluation of patient satisfaction after the use of educational materials. RESULTS: An educational manual was developed in compliance with the main requirements for effectiveness of educational materials referring to content, structure, language, layout and illustrations. The usefulness of the educational manual and patient satisfaction were evaluated by a sample group of 20 women with GDM. Approximately 95% agreed or strongly agreed that the information in the educational manual was useful. The patients' assessment of the understanding and readability of the written materials showed a satisfaction rate of 85%. The overall assessment for the educational materials was very high - excellent (65%), very good (30%) and good (5%). CONCLUSION: The provision of educational materials on GDM can enhance pregnant women's health literacy as well as their responsibility, motivation and attitude to their personal health.

Regulatory Requirements for Food Supplements in the European Union and Bulgaria.

Data provided by the European Commission show that public expenditures for food supplements have been constantly increasing over the last decade. The aim of the present study was to analyze the major food supplements regulations in the European Union and in Bulgaria. Relevant publications were searched and found in MEDLINE/PubMed, Scopus Database, Web of Knowledge, and in Internet-based search with predefined keywords. Numerous authors support the opinion that there is a real risk that low quality products may be distributed in countries with poor production control. Bulgarian national legislation have 6 regulations with different legal force for provision of healthy and safe food supplements on the market. Currently, the European Community is concerned about food products, including FS, launched on the market because the citizens require reliable protection of their health. This concern provoked the European Parliament and the Council to undertake a number of legislative initiatives in the field of production and control of food products. It is necessary to set more precise quality and safety criteria in future strategies associated with those products.

The 5-minute Apgar Score as a Prognostic Factor for Development and Progression of Retinopathy of Prematurity.

BACKGROUND: A low Apgar score at 5 minutes has been shown to be a risk factor for development of retinopathy of prematurity (ROP). AIM: To examine the prognostic value of Apgar score at 5 minutes for development and progression of ROP. MATERIALS AND METHODS: The study included 132 preterm infants who were screened from 4th week of life onward. Of these, 118 newborns were given Apgar score at 5 minutes. The prognostic significance of this index was studied as an absolute value and as a value ≤ 6. The patients were divided into two groups: group I had no evidence of ROP (n=82) and group II had some signs of ROP (n = 36). Group II was further divided into group IIA - spontaneously regressed cases (n=22), and group IIB with cases which progressed to treatment stages (n=14). We investigated 15 maternal and 20 newborn presumable risk factors for development and progression of ROP. Mann-Whitney U test, χ2 or Fisher's exact test were used in the statistical analysis. Logistic regression was performed to find significant and independent risk factors for manifestation and progression of ROP. RESULTS: A low 5-minute Apgar score and an Apgar score of 6 or less at 5 minutes were not statistically significant risk factors of ROP (р=0.191, р=0.191, respectively), but were significant risk factors for the manifested ROP to progress to stages requiring treatment (p=0.046, р=0.036, respectively). CONCLUSION: An Apgar score at 5 minutes of 6 or less was a significant and independent risk factor for progression of ROP to stages requiring treatment.

Is There a Link Between Changes in Levels of Hepcidin and Stroke?

BACKGROUND: Iron is an essential element for the living body. It is well known that iron homeostasis disorders are important in two ways--its deficiency and its overload lead to several pathologies. METHODS: We measured 17 patients with iron deficiency anemia (IDA); 19 with anemia of chronic diseases (ACD); 15 with ischemic stroke (IS). The results were compared to a previously selected control group. For evaluation of iron metabolism status, we measured serum iron levels, ferritin, and soluble transferrin receptors. For inflammation, serum interleukin-6 and hsCRP were measured. Serum hepcidin quantification was performed using a previously validated immunosorbent method. Ferritin was measured by an ECLIA method; serum iron on AAS; hsCRP using a nephelometric analysis. RESULTS: We found statistically significant elevated serum hepcidin levels in patients with ACD and IS compared to the control group (p < 0.001). Patients with IDA had statistically significant lower hepcidin levels compared to the control group (p < 0.001). Serum ferritin levels in the IS group was higher compared to the control and other groups (p < 0.001). The lowest ferritin concentrations were established in the IDA group compared to the control (p < 0.001). We found a strong correlation between serum hepcidin and ferritin levels in the IS group (r = 0.583; p < 0.001). CONCLUSIONS: Quantification of serum hepcidin levels might be used as a link for prediction of acute ischemic stroke and future therapeutic influences.

ADMA--a Possible Marker for Early Therapeutic Outcome in Acute Stroke.

BACKGROUND: Ischemic acute stroke is a leading cause for mortality and invalidity in recent years. Clinical trials show the role of ADMA as endogenous inhibitor of nitric oxide synthase and its connection to acute stroke. An early decrease of serum ADMA levels might help in recovery of the blood stream in patients with acute stroke and non-affective changes in the brain. METHODS: We compared 18 patients with acute stroke before and after thrombolysis and 21 patients (without history of cardiovascular disease, diabetes, kidney and liver injury, non-smokers) before and after thrombolysis. All results were compared to 30 healthy persons. Patients were evaluated by NIHSS, with ultrasound, CT and laboratory methods (traditional risk factors and CRP, D-dimmer, homocysteine, and ADMA). RESULTS: Classic vascular factors showed statistical significance in patients with acute stroke. Serum hsCRP levels and D-dimer in our study showed no connection to acute stroke. We found a statistically significant correlation in patients with stroke between ADMA and homocysteine levels (r = 0.469, p < 0.001). We found no significant difference between basic serum ADMA concentrations in groups with stroke who underwent different treatment (r = -0.449, p < 0.001). In patients with thrombolysis ADMA concentrations are reduced earlier, which also shows that earlier clinical recovery leads to no brain damaging effects. CONCLUSIONS: Through its pathophysiological changes, ADMA might be a predictor for acute stroke (along with already known risk factors) and can be a marker for the outcome of stroke, depending on the treatment.

Serum hepcidin levels in Bulgarian population.

BACKGROUND: Hepcidin is a 25-aminoacid cysteine-rich iron regulating peptide. Hepcidin quantification in human serum provides new insights for the pathogenesis of disorders of iron homeostasis. This study describes an ELISA immunoassay for hepcidin quantification in human serum and reference ranges for Bulgarian population. METHODS: We used a sandwich ELISA method from USCN Life Science inc. that consists of ready to use, pre-coated 96-well strip plate with 2 antihepcidin-25 monoclonal antibodies. A recombinant Hepcidin in 16 µg/L concentration is used as a standard. We correlated ELISA results of hepcidin-25 measurements in healthy population to ferritin, hemoglobin concentration in reticulocytes, transferrin, and iron levels. RESULTS: The sandwich ELISA was highly specific for hepcidin-25. We found that serum hepcidin levels for Bulgarian population are 3.052 µg/L - 37.750 µg/L, which is quite similar to that established by WCX-TOF MS from the Laboratory of Genetic, Endocrine and Metabolic Diseases; Dept. of Laboratory Medicine, Radbound University Medical Centre; Nijmegen, The Netherlands. Ferritin levels and hemoglobin concentration in reticulocytes correlated significantly to serum hepcidin levels (0.3 < r < 0.5, p < 0.010). Transferrin levels showed negative and no significant correlation to hepcidin in serum (r = -0.111). CONCLUSIONS: The use of two monoclonal antibodies in a sandwich ELISA format provides a reliable, reproducible, and not very expensive method for measuring serum concentrations of the bioactive form of hepcidin in Bulgarian laboratory practice.

Approaching the asymptotic regime of rapidly rotating convection: boundary layers versus interior dynamics.

Rapidly rotating Rayleigh-Bénard convection is studied by combining results from direct numerical simulations (DNS), laboratory experiments, and asymptotic modeling. The asymptotic theory is shown to provide a good description of the bulk dynamics at low, but finite Rossby number. However, large deviations from the asymptotically predicted heat transfer scaling are found, with laboratory experiments and DNS consistently yielding much larger Nusselt numbers than expected. These deviations are traced down to dynamically active Ekman boundary layers, which are shown to play an integral part in controlling heat transfer even for Ekman numbers as small as 10^{-7}. By adding an analytical parametrization of the Ekman transport to simulations using stress-free boundary conditions, we demonstrate that the heat transfer jumps from values broadly compatible with the asymptotic theory to states of strongly increased heat transfer, in good quantitative agreement with no-slip DNS and compatible with the experimental data. Finally, similarly to nonrotating convection, we find no single scaling behavior, but instead that multiple well-defined dynamical regimes exist in rapidly rotating convection systems.

Metal-induced point defects in DNA: model and mechanisms.

The aim of this work was to study the role of H3O+ and transition-metal (TM) ions in keto-enol and amino-imino tautomeric transitions in DNA base pairs and depurination. In this regard, we discuss the thermodynamic model of ion-DNA interactions and UV display of double-proton transfer (DPT) in GC. The probabilities and energies of rare tautomeric forms of GC pairs in DNA induced by H3O+ and TMwere determined being in the range from0.02 (forMg2+) to 1 ( forCu2+), and from 0 kcal/m (for Cu2+) to 2.3 kcal/m (for Mg2+), respectively. It was shown that 3'ACC5'/5'TGG3' site of DNA double helix, which corresponds to the only triplet 5'UGG3' of RNA that codes the most valuable amino acid tryptophan, is a good target for TM ions to attack. It was also shown that the only way to obtain the tryptophan-coding 5'UGG3' triplet in RNA via transition-type G --> A point mutation caused by TM ions is their interaction with the site of a DNA double helix, which corresponds to 5'CGG3' triplet of RNA that codes arginine.