Thermal and mechanical properties of recycled poly(Lactic acid)

Biodegradable polymers have experienced increased attention in recent years because of their wide range of applications in biomedical, packaging and agriculture fields. PLA, poly(lactic acid), is a linear aliphatic biodegradable thermoplastic polyester, with good mechanical properties, thermal stability, processability and low environmental impact, widely used as an alternative to conventional polymers. PLA products can be recycled after use either by remelting and reprocessing the material, or by hydrolysis to basic lactic acid [1]. The object of this communication is the study of the possible variation in physical properties induced by sub sequent reprocessing cycles of PLA

The effect of temperature and enzyme concentration in the transesterification process of synthetic microalgae oil

Throughout the world, the fossil fuel has supplied around the 80% of the energetic requirements, in Colombia alone 95.1% of energetic demand is made by the transportation sector solely, supplied by oil, kerosene, gasoline and diesel, this sector has an extremely small participation with biofuel of 3%, which is represented only by biodiesel. Microalgae had been proposed as biofactories with a remarkable third generation biofuels production. The culture of the microorganism comprehends interesting characteristics as countless environments where its natural growth could be replicated in fresh, salty and even sewage waters, with a higher growth rate and a higher oil production. The implementation of enzymes in the transesterification process have generated a good curiosity in the field, due to its mild reactions conditions, lesser energetic requirements, a high standard in the selection of the enzymes with the objective of avoiding the formation of soaps, creating in this way cleaner products and sub-products, in which the separation of the phases biodiesel/glycerol, give the possibility to recuperate the bio catalyzer and high output of reactions. However, the high volume of medium required to obtain lipids is one of the major drawbacks to test the viability of these enzymes. The present study aims to design an enzymatic transesterification process for the production of biodiesel form synthetic Chlorella oil. The synthetic oil was designed according to the lipid profile of C 16:0, C16:1, C18:0, C18:1, C18:2 and C18:3 from Chlorella spp CHL2 cultured on Bold Basal media under limited concentrations of NaNO3. The enzymatic transesterification efficiency was evaluated by the implementation of a 22 experimental factorial design (temperature and lipase concentration) under a 3: 1 molar ratio of alcohol:oil and a fixed reaction time of 6 hours. The obtained results show that, in order to obtain superior yields of biodiesel (>91%) the transesterification process must be carried out under temperature conditions close to 38°C and lipase concentrations of 5%

A Primer on Resonances in Quantum Mechanics

After a pedagogical introduction to the concept of resonance in classical and quantum mechanics, some interesting applications are discussed. The subject includes resonances occurring as one of the effects of radiative reaction, the resonances involved in the refraction of electromagnetic waves by a medium with a complex refractive index, and quantum decaying systems described in terms of resonant states of the energy. Some useful mathematical approaches like the Fourier transform, the complex scaling method and the Darboux transformation are also reviewed.Comment: 28 pages, 9 figures, lectures presented at the Advanced Summer School in Physics 2008, Cinvestav, Mexic

Application of Chlorella sp. and Scenedesmus sp. in the bioconversion of urban leachates into industrially relevant metabolites

This paper explores the ability of Chlorella sp. and Scenedesmus sp. to convert landfill leachates into usable metabolites. Different concentrations (0.5, 1, 5, and 10% v/v) of leachate coupled with an inorganic carbon source (Na2CO3, and NaHCO3) were tested to improve biomass production, metabolites synthesis, and removal of NO3 and PO4 . The result shows that both strains can effectively grow in media with up to 5% (v/v) leachate, while significantly reducing the concentrations of NO3, and PO4 (80 and 50%, respectively). The addition of NaHCO3 as a carbon source improved the final concentration of biomass, lipids, carbohydrates, and the removal of NO3 and PO4 in both strains

Enhanced tunable second harmonic generation from twistable interfaces and vertical superlattices in boron nitride homostructures

Broken symmetries induce strong even-order nonlinear optical responses in materials and at interfaces. Unlike conventional covalently bonded nonlinear crystals, van der Waals (vdW) heterostructures feature layers that can be stacked at arbitrary angles, giving complete control over the presence or lack of inversion symmetry at a crystal interface. Here, we report highly tunable second harmonic generation (SHG) from nanomechanically rotatable stacks of bulk hexagonal boron nitride (BN) crystals and introduce the term twistoptics to describe studies of optical properties in twistable vdW systems. By suppressing residual bulk effects, we observe SHG intensity modulated by a factor of more than 50, and polarization patterns determined by moiré interface symmetry. Last, we demonstrate greatly enhanced conversion efficiency in vdW vertical superlattice structures with multiple symmetry-broken interfaces. Our study paves the way for compact twistoptics architectures aimed at efficient tunable frequency conversion and demonstrates SHG as a robust probe of buried vdW interfaces

A probabilistic method for the operation of three-phase unbalanced active distribution networks

YesThis paper proposes a probabilistic multi-objective optimization method for the operation of three-phase distribution networks incorporating active network management (ANM) schemes including coordinated voltage control and adaptive power factor control. The proposed probabilistic method incorporates detailed modelling of three-phase distribution network components and considers different operational objectives. The method simultaneously minimizes the total energy losses of the lines from the point of view of distribution network operators (DNOs) and maximizes the energy generated by photovoltaic (PV) cells considering ANM schemes and network constraints. Uncertainties related to intermittent generation of PVs and load demands are modelled by probability density functions (PDFs). Monte Carlo simulation method is employed to use the generated PDFs. The problem is solved using ɛ-constraint approach and fuzzy satisfying method is used to select the best solution from the Pareto optimal set. The effectiveness of the proposed probabilistic method is demonstrated with IEEE 13- and 34- bus test feeders

Prevalence and clinical outcomes of dystrophin-associated dilated cardiomyopathy without severe skeletal myopathy

Aims: Dilated cardiomyopathy (DCM) associated with dystrophin gene (DMD) mutations in individuals with mild or absent skeletal myopathy is often indistinguishable from other DCM forms. We sought to describe the phenotype and prognosis of DMD associated DCM in DMD mutation carriers without severe skeletal myopathy. Methods and results: At 26 European centres, we retrospectively collected clinical characteristics and outcomes of 223 DMD mutation carriers (83% male, 33 ± 15 years). A total of 112 individuals (52%) had DCM at first evaluation [n = 85; left ventricular ejection fraction (LVEF) 34 ± 11.2%] or developed DCM (n = 27; LVEF 41.3 ± 7.5%) after a median follow-up of 96 months (interquartile range 5–311 months). DCM penetrance was 45% in carriers older than 40 years. DCM appeared earlier in males and was independent of the type of mutation, presence of skeletal myopathy, or elevated serum creatine kinase levels. Major adverse cardiac events (MACE) occurred in 22% individuals with DCM, 18% developed end-stage heart failure and 9% sudden cardiac death or equivalent. Skeletal myopathy was not associated with survival free of MACE in patients with DCM. Decreased LVEF and increased left ventricular end-diastolic diameter at baseline were associated with MACE. Individuals without DCM had favourable prognosis without MACE or death during follow-up. Conclusions: DMD-associated DCM without severe skeletal myopathy is characterized by incomplete penetrance but high risk of MACE, including progression to end-stage heart failure and ventricular arrhythmias. DCM onset is the major determinant of prognosis with similar survival regardless of the presence of skeletal myopathy

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Clinical Risk Score to Predict Pathogenic Genotypes in Patients With Dilated Cardiomyopathy

Background: Although genotyping allows family screening and influences risk-stratification in patients with nonischemic dilated cardiomyopathy (DCM) or isolated left ventricular systolic dysfunction (LVSD), its result is negative in a significant number of patients, limiting its widespread adoption. Objectives: This study sought to develop and externally validate a score that predicts the probability for a positive genetic test result (G+) in DCM/LVSD. Methods: Clinical, electrocardiogram, and echocardiographic variables were collected in 1,015 genotyped patients from Spain with DCM/LVSD. Multivariable logistic regression analysis was used to identify variables independently predicting G+, which were summed to create the Madrid Genotype Score. The external validation sample comprised 1,097 genotyped patients from the Maastricht and Trieste registries. Results: A G+ result was found in 377 (37%) and 289 (26%) patients from the derivation and validation cohorts, respectively. Independent predictors of a G+ result in the derivation cohort were: family history of DCM (OR: 2.29; 95% CI: 1.73-3.04; P < 0.001), low electrocardiogram voltage in peripheral leads (OR: 3.61; 95% CI: 2.38-5.49; P < 0.001), skeletal myopathy (OR: 3.42; 95% CI: 1.60-7.31; P = 0.001), absence of hypertension (OR: 2.28; 95% CI: 1.67-3.13; P < 0.001), and absence of left bundle branch block (OR: 3.58; 95% CI: 2.57-5.01; P < 0.001). A score containing these factors predicted a G+ result, ranging from 3% when all predictors were absent to 79% when ≥4 predictors were present. Internal validation provided a C-statistic of 0.74 (95% CI: 0.71-0.77) and a calibration slope of 0.94 (95% CI: 0.80-1.10). The C-statistic in the external validation cohort was 0.74 (95% CI: 0.71-0.78). Conclusions: The Madrid Genotype Score is an accurate tool to predict a G+ result in DCM/LVSD