Do not use the Friedewald formula to calculate LDL‐cholesterol in hypercholesterolaemic rats

Reputable calculations such as the Friedewald formula are used extensively to determine LDL‐cholesterol (LDL‐C) values from known total cholesterol, triacylglycerol and HDL‐cholesterol (HDL‐C) levels. To the best of our knowledge, however, the validity of this equation has not yet been confirmed in rats. The aim of the present study is to give some insights as to why this formula must be used carefully in rats, and to find cut‐off points below which this formula can be considered reliable. Sera of 54 rats with different cholesterol, triacylglycerol and HDL‐C levels were tested. LDL was isolated by ultracentrifugation and LDL‐C measured by an enzymatic colorimetric method and compared against LDL‐C obtained by the formula. In rats whose serum cholesterol was <100 mg/dL, or whose HDL‐C constituted ≥75% of total cholesterol, or whose cholesterol/phospholipids ratio was <1, or whose serum did not contain β‐VLDL, LDL‐C obtained by both methods did not significantly differ. Under other conditions, however, and particularly in hypercholesterolaemic rats who did present β‐VLDL, the results clearly show that the Friedewald formula overestimates LDL‐C levels. In conclusion, (VLDL + LDL)‐C instead of VLDL‐C and LDL‐C must be used when ultracentrifugation or other alternative methods are not available to measure LDL‐C in hypercholesterolaemic rats.     

Trimmed means for functional data

In practice, the use of functional data is often preferable to that of large finitedimensional vectors obtained by discrete approximations of functions. In this paper a new concept of data depth is introduced for functional data. The aim is to measure the centrality of a given curve within a group of curves. This concept is used to define ranks and trimmed means for functional data. Some theoretical and practical aspects are discussed and a simulation study is given. The results show a good performance of our method, in terms of efficiency and robustness, when compared with the mean. Finally, a real-data example based on the Nasdaq 100 index is discussed.     

Self-similar Expansion of the Density Profile in a Turbulent Bose-Einstein Condensate

In a recent study we demonstrated the emergence of turbulence in a trapped Bose-Einstein condensate of ⁸⁷Rb atoms. An intriguing observation in such a system is the behavior of the turbulent cloud during free expansion. The aspect ratio of the cloud size does not change in the way one would expect for an ordinary non-rotating (vortex-free) condensate. Here we show that the anomalous expansion can be understood, at least qualitatively, in terms of the presence of vorticity distributed throughout the cloud, effectively counteracting the usual reversal of the aspect ratio seen in free time-of-flight expansion of non-rotating condensates.     

Superabsorbent hydrogel composites with a focus on hydrogels containing nanofibers or nanowhiskers of cellulose and chitin

The development of superabsorbent hydrogels (SHs) is a very important issue in both academic and industrial fields because of their applications in several technologies. The impressive number of publications dealing with SH confirms this statement: a quick search in the ISI (Web of Science) database under the words superabsorbent hydrogels revealed more than 600 articles published, with about 80% of those published in last decade. Current studies on the development of SHs have focused on the formulation of highly functional materials with enhanced properties for suitable applications in different fields. In light of this, the incorporation of microsized or nanosized materials in SH formulations has been explored as a very attractive strategy for tailoring desired properties. In this review, we discuss relevant aspects of the current knowledge of SHs and nanocomposite polymer hydrogels, mainly those based on chitin and cellulose nanocrystals (fibers and/or whiskers), bringing to light some structure–property relationships and future trends. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39725.     

Advanced oxidation processes applied to tannery wastewater containing Direct Black 38--elimination and degradation kinetics

The application of advanced oxidation processes (H(2)O(2)/UV, TiO(2)/H(2)O(2)/UV and TiO(2)/UV) to treat tannery wastewater was investigated. The experiments were performed in batch and continuous UV reactors, using TiO(2) as a catalyst. The effect of the hydrogen peroxide concentration on the degradation kinetics was evaluated in the concentration range 0-1800 mg L(-1). We observed that the degradation rate increased as the hydrogen peroxide increased, but excessive H(2)O(2) concentration was detrimental because it acted as a hydroxyl radical scavenger since it can compete for the active sites of the TiO(2). In the H(2)O(2)/UV treatment, the COD removal reached around 60% in 4 h of reaction, indicating that the principal pollutants were chemically degraded as demonstrated by the results for BOD, COD, nitrate, ammonium and analysis of the absorbance at 254 nm. Artemia salina toxicity testing performed in parallel showed an increase in toxicity after AOP treatment of the tannery wastewater.     

Enhanced spin-valve effect in magnetically doped carbon nanotubes

Spin valves made of nanotubes contacted to magnetic electrodes may display significant values of magnetoresistance but are limited by the restricted capacity for spin injection into the tube and by the unwanted spin-flip scattering caused by magnetic impurities. We propose an alternative route to produce the spin-valve effect which (a) does not involve magnetic electrodes, avoiding the spin injection limitation, and (b) uses magnetically coupled impurities to generate an efficient spin filter that enhances the magnetoresistance by orders of magnitude. Furthermore, we predict that substitutional Mn impurities on metallic nanotubes will generate enormously large values of magnetoresistance.     

Impact of sweetness on the sensory acceptance of passion fruit nectar in Brazilian geographic regions

Passion fruit is the fourth most consumed fruit by the Brazilian population, especially in the form of juice, usually associated with the addition of sucrose. This study aimed to evaluate the ideal sucrose concentration, and its impact on the consumer's acceptance of passion fruit nectar, sweetened with non-caloric sweeteners as sucrose replacers in five Brazilian geographic regions. The acceptance scores evaluated by anova and Tukey's Honestly Significant Difference test indicated that sucralose-sweetened samples were the most accepted, with no differences from the sucrose-sweetened sample (P < 0.05), with a positive purchase intention in the five regions studied (>50%). However, differences in the acceptance scores were observed for the other sweeteners among the regions. Despite the difference in the sweetness perception among the Brazilian geographic regions, it may not be the only determining factor in the acceptance of passion fruit nectar sweetened with non-caloric sweeteners.     

Two‐step synthesis and properties of a magnetic‐field‐sensitive modified maltodextrin‐based hydrogel

A magnetic‐field‐sensitive modified maltodextrin‐based hydrogel (ferrogel) was synthesized. Fourier transform infrared and ¹³C‐CP/MAS NMR spectral analyses confirmed the efficiency of the gelling process. X‐ray diffraction analysis revealed the appearance of new crystalline planes in the hydrogel diffractograms after embedding of magnetite nanoparticles. Magnetization curves and Mössbauer analysis revealed that the magnetic hydrogel has a high lattice strain due to bonded iron atom covalence. Moreover, some magnetite molecules embedded in the hydrogel ensure a degree of paramagnetism and iron atoms exhibiting oxidation states alternating between 2 and 3 in the final material. Scanning electron microscopy and energy‐dispersive X‐ray analysis revealed that no phase separation occurred between the magnetite nanoparticles and crosslinked hydrogel, indicating excellent dispersion throughout the hydrogel. Moreover, the average pore sizes decreased on increasing the amount of magnetite inside the polymer network. The results of compression stress versus strain revealed that the elasticity of the magnetic hydrogel was increased on increasing the amount of magnetite nanoparticles. Finally, kinetic studies revealed that the diffusion mechanism of water in the hydrogel is driven by anomalous release with a tendency towards the occurrence of macromolecular relaxation. Copyright © 2011 Society of Chemical Industry     

Antimicrobial Activity of Chitosan Derivatives Containing N-Quaternized Moieties in Its Backbone: A Review

Chitosan, which is derived from a deacetylation reaction of chitin, has attractive antimicrobial activity. However, chitosan applications as a biocide are only effective in acidic medium due to its low solubility in neutral and basic conditions. Also, the positive charges carried by the protonated amine groups of chitosan (in acidic conditions) that are the driving force for its solubilization are also associated with its antimicrobial activity. Therefore, chemical modifications of chitosan are required to enhance its solubility and broaden the spectrum of its applications, including as biocide. Quaternization on the nitrogen atom of chitosan is the most used route to render water-soluble chitosan-derivatives, especially at physiological pH conditions. Recent reports in the literature demonstrate that such chitosan-derivatives present excellent antimicrobial activity due to permanent positive charge on nitrogen atoms side-bonded to the polymer backbone. This review presents some relevant work regarding the use of quaternized chitosan-derivatives obtained by different synthetic paths in applications as antimicrobial agents.