The effect of layer’s thickness on the optical response of superlattices

We apply the Theory of Finite Periodic Systems to study the photoluminescent behavior of superlattices. Using this formalism, where intra-subband energy levels are neatly identified, we study the optical response for different barrier and well thicknesses, and show that this quantity is very sensitive to small changes in the superlattice parameters. Varying the barrier thickness (for fixed well-width), or the well-width (for constant barrier thickness), the intensities of the relevant PL-peaks change drastically. We make clear also that this highly accurate formalism can be used to design optimal superlattice-optoelectronic devices.     

A morphological view of the relationship between indirect flight muscle maturation and the flying needs of two species of advanced eusocial bees

This paper describes the flight muscles changes in relation to the age/function of the adult members of the colonies of two advanced species of eusocial bees: Apis mellifera (Apini) and Scaptotrigona postica (Meliponini). Here, are reported the results obtained through transmission electron microscopy studies, first describing a general overview of the flight muscle ultrastructure and second reporting on the ultrastructural changes that occur along the life stages/functions of workers, queens and males. The workers emerge with immature flight muscles, and the maturation takes about 20 days. In contrast, queens and males emerged with more advanced muscle differentiation, similar to workers after the 20 days of maturation. In both forager workers and laying queens, flight muscles showed signs of senescence, but not in sexually mature males. The differences among life phases, individual classes and species are discussed in relation to their functions in the colony.     

Differential expression of myogenic regulatory factor MyoD in pacu skeletal muscle (Piaractus mesopotamicus Holmberg 1887: Serrasalminae, Characidae, Teleostei) during juvenile and adult growth phases

Skeletal muscle is the edible part of the fish. It grows by hypertrophy and hyperplasia, events regulated by differential expression of myogenic regulatory factors (MRFs). The study of muscle growth mechanisms in fish is very important in fish farming development. Pacu (Piaractus mesopotamicus) is one of the most important food species farmed in Brazil and has been extensively used in Brazilian aquaculture programs. The aim of this study was to analyze hyperplasia and hypertrophy and the MRF MyoD expression pattern in skeletal muscle of pacu (P. mesopotamicus) during juvenile and adult growth stages. Juvenile (n = 5) and adult (n = 5) fish were anaesthetized, sacrificed, and weight (g) and total length (cm) determined. White dorsal region muscle samples were collected and immersed in liquid nitrogen. Transverse sections (10 μm thick) were stained with Haematoxilin–Eosin (HE) for morphological and morphometric analysis. Smallest fiber diameter from 100 muscle fibers per animal was calculated in each growth phase. These fibers were grouped into three classes (<20, 20–50, and >50 μm) to evaluate hypertrophy and hyperplasia in white skeletal muscle. MyoD gene expression was determined by semi-quantitative RT-PCR. PCR products were cloned and sequenced. Juvenile and adult pacu skeletal muscle had similar morphology. The large number of <20 μm diameter muscle fibers observed in juvenile fish confirms active hyperplasia. In adult fish, most fibers were over 50 μm diameter and denote more intense muscle fiber hypertrophy. The MyoD mRNA level in juveniles was higher than in adults. A consensus partial sequence for MyoD gene (338 base pairs) was obtained. The Pacu MyoD nucleotide sequence displayed high similarity among several vertebrates, including teleosts. The differential MyoD gene expression observed in pacu white muscle is possibly related to differences in growth patterns during the phases analyzed, with hyperplasia predominant in juveniles and hypertrophy in adult fish. These results should provide a foundation for understanding the molecular control of skeletal muscle growth in economically important Brazilian species, with a view to improving production quality.     

Selective Cytotoxicity of Portuguese Propolis Ethyl Acetate Fraction towards Renal Cancer Cells

Renal cell carcinoma is the most lethal cancer of the urological system due to late diagnosis and treatment resistance. Propolis, a beehive product, is a valuable natural source of compounds with bioactivities and may be a beneficial addition to current anticancer treatments. A Portuguese propolis sample, its fractions (n-hexane, ethyl acetate, n-butanol and water) and three subfractions (P1–P3), were tested for their toxicity on A498, 786-O and Caki-2 renal cell carcinoma cell lines and the non-neoplastic HK2 kidney cells. The ethyl acetate fraction showed the strongest toxicity against A498 (IC₅₀ = 0.162 µg mL⁻¹) and 786-O (IC₅₀ = 0.271 µg mL⁻¹) cells. With similar toxicity against 786-O, P1 (IC₅₀ = 3.8 µg mL⁻¹) and P3 (IC₅₀ = 3.1 µg mL⁻¹) exhibited greater effect when combined (IC₅₀ = 2.5 µg mL⁻¹). Results support the potential of propolis and its constituents as promising coadjuvants in renal cell carcinoma treatment.     

Needle Trap Device-GC-MS for Characterization of Lung Diseases Based on Breath VOC Profiles

Volatile organic compounds (VOCs) have been assessed in breath samples as possible indicators of diseases. The present study aimed to quantify 29 VOCs (previously reported as potential biomarkers of lung diseases) in breath samples collected from controls and individuals with lung cancer, chronic obstructive pulmonary disease and asthma. Besides that, global VOC profiles were investigated. A needle trap device (NTD) was used as pre-concentration technique, associated to gas chromatography-mass spectrometry (GC-MS) analysis. Univariate and multivariate approaches were applied to assess VOC distributions according to the studied diseases. Limits of quantitation ranged from 0.003 to 6.21 ppbv and calculated relative standard deviations did not exceed 10%. At least 15 of the quantified targets presented themselves as discriminating features. A random forest (RF) method was performed in order to classify enrolled conditions according to VOCs’ latent patterns, considering VOCs responses in global profiles. The developed model was based on 12 discriminating features and provided overall balanced accuracy of 85.7%. Ultimately, multinomial logistic regression (MLR) analysis was conducted using the concentration of the nine most discriminative targets (2-propanol, 3-methylpentane, (E)-ocimene, limonene, m-cymene, benzonitrile, undecane, terpineol, phenol) as input and provided an average overall accuracy of 95.5% for multiclass prediction.     

Fertility and Iron Bioaccumulation in Drosophila melanogaster Fed with Magnetite Nanoparticles Using a Validated Method

Research on nanomaterial exposure-related health risks is still quite limited; this includes standardizing methods for measuring metals in living organisms. Thus, this study validated an atomic absorption spectrophotometry method to determine fertility and bioaccumulated iron content in Drosophila melanogaster flies after feeding them magnetite nanoparticles (Fe₃O₄NPs) dosed in a culture medium (100, 250, 500, and 1000 mg kg⁻¹). Some NPs were also coated with chitosan to compare iron assimilation. Considering both accuracy and precision, results showed the method was optimal for concentrations greater than 20 mg L⁻¹. Recovery values were considered optimum within the 95–105% range. Regarding fertility, offspring for each coated and non-coated NPs concentration decreased in relation to the control group. Flies exposed to 100 mg L⁻¹ of coated NPs presented the lowest fertility level and highest bioaccumulation factor. Despite an association between iron bioaccumulation and NPs concentration, the 500 mg L⁻¹ dose of coated and non-coated NPs showed similar iron concentrations to those of the control group. Thus, Drosophila flies’ fertility decreased after NPs exposure, while iron bioaccumulation was related to NPs concentration and coating. We determined this method can overcome sample limitations and biological matrix-associated heterogeneity, thus allowing for bioaccumulated iron detection regardless of exposure to coated or non-coated magnetite NPs, meaning this protocol could be applicable with any type of iron NPs.     

A voltammetric method for diuron determination in river water

A sensitive, simple, fast, and inexpensive method for determining diuron in water using square wave voltammetry and a glassy carbon electrode is presented. This method was developed to evaluate diuron contamination in river waters close to sugarcane cultivation, located in the metropolitan region of João Pessoa, in the state of Paraíba, Brazil. An analytical curve with a linear response ranging from 38.5–115.0 nmol L⁻¹ (r² = 0.993), a LOD equal 0.2 nmol L⁻¹, and recovery rates from 88.0 to 108.0 %. The proposed method does not require any previous chemical treatment of the sample, thus contributing to green analytical chemistry.     

β-Cyclodextrin PAMAM Dendrimer Surface Doped with Silver and Hexacyanoferrate (III) and its Applications for Dopamine Detection in Synthetic Samples

A synthesis of β-cyclodextrin (β-Cd) functionalized with polyamide dendrimer PAMAM G.0 complexed with silver and potassium hexacyanoferrate (III) forming a mixed-valence complex (β-Cd-PAMAM-Ag/Fe) was proposed. This material was characterized by scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), X-Ray diffraction (XRD), Energy Dispersion Spectroscopy (EDS) and Electron Paramagnetic Resonance (EPR). The hybrid complex was electrochemically investigated using cyclic voltammetry and some parameters (electrolyte, concentration of electrolyte, pH and scan rate) were evaluate in order to obtain optimum analytical responses. The β-Cd-PAMAM-Ag/Fe material was successfully applied in the electrocatalytic oxidation of dopamine (DOP) using Cyclic Voltammetry (CV) and Square Wave Voltammetry (SWV).