Recent advances on lactose intolerance: Tolerance thresholds and currently available answers

The genetically programmed reduction in lactase activity during adulthood affects 70% of the world adult population and can cause severe digestive disorders, which are the sign of lactose intolerance. Lactose intolerance symptoms vary depending on the residual lactase activity, the small bowel transit time, and especially the amount of ingested lactose. To formulate dairy products suitable for the vast majority of lactose intolerants, it is essential to define lactose intolerance threshold. A recent meta-analysis permitted to show that almost all lactose intolerants tolerate 12 g of lactose in one intake and approximately 18 g of lactose spread over the day. The prevalence and severity of lactose intolerance are probably overestimated by the general public. This misconception usually leads to an unnecessary reduction of dairy foodstuff consumption. Nevertheless, dairy products are essential for health mainly due to their calcium content and the positive influence of probiotic bacteria. The formulation of dairy products suitable for most intolerant and suspicious subjects seems necessary. The use of exogenous enzyme preparations, as well as the consumption of lactose-free products or products rich in probiotic bacteria are proposed as symptom-reducing strategies.     

A Fluorometric Enzymatic Assay for Quantification of Steryl Glucosides in Biodiesel

Steryl glucosides (SG) are common contaminants in biodiesel that form precipitates, which form and cause problems due to fouling during transport and storage. Therefore, their quantification is necessary to assess the quality of this fuel. The methods currently available for SG analysis require expensive instrumentation, need a previous concentration step by solid‐phase extraction (SPE) or are of limited use for the quantitative assessment. We developed an enzymatic method for SG quantification in biodiesel samples based on the hydrolysis of the glucoside catalyzed by a broadly specific beta glucosidase and the subsequent determination of the glucose released by the reaction. The method is non‐expensive, sensitive and was adapted to 96‐well format fluorescence plate reader, making it useful for the parallel assay of multiple samples. The enzymatic assay presented here represent a valuable tool for both quality control and the development of improved biodiesel production and purification procedures.     

Spatial and temporal distribution of ichthyoplankton during an unusual period of low flow in a tributary of the São Francisco River,Brazil

Flow‐dependent fish specialists require specific conditions for reproduction, so the success and reproductive intensity of these animals are determined by the flood regime. Thus, this study investigated the spatial and temporal reproductive patterns of fish, especially migratory Prochilodus species (flow‐dependent specialists) in an unusual period of low flow in the Pará River sub‐basin, one of the main tributaries of the upper São Francisco River. For this, ichthyoplankton collections were carried out between November 2013 and February 2014. Data were analysed considering the spatial and temporal variations in density of eggs and larvae for the upper, middle, and lower portions of the Pará River sub‐basin, and correlating this to some environmental variables. The results showed that the small headwater stretch of the Pará River is one relevant spawning area for migratory fish species. However, this area is isolated by the Cajuru reservoir, which makes it uncertain the recruitment of these embryos, due to interruption of natural drift between spawning/nursery areas caused for reservoirs. Larvae of newly hatched migratory species found in tributaries of the lower Pará River sub‐basin also indicate these species use these tributaries as spawning grounds and migratory routes. The period in which the research was conducted represented the most atypical low flow, one in the last 75 years, resulting in the low variability in the environmental parameters. Although few parameters increased briefly in this low flow period influenced by greater rainfall in December, this precipitation was possibly responsible for the final gonadal maturation and spawning of migratory species.     

Thermoelectric and mechanical properties of melt spun and spark plasma sintered n-type Yb- and Ba-filled skutterudites

Here we present thermoelectric and mechanical properties of n-type filled-skutterudites produced by a combination of melt spinning of pre-melted charges with subsequent consolidation by spark plasma sintering, a process we refer to as MS-SPS. This combination of processing steps leads to phase-pure n-type filled-skutterudites and obviates more energy and time intensive annealing steps. We show that both the thermoelectric properties and the tensile fracture strength compare favorably to materials made by traditional methods. The process is scalable to at least 80 g billets, such that the transport properties measured on test bars harvested from these larger billets compare favorably to those measured on lab-scale billets (5 g total billet mass). ZT values approaching 1.1 at 750 K were observed in materials made by MS-SPS. In addition, the tensile fracture strength of test bars cut from an 80 g billet is ∼128 MPa at room temperature and decreases with increasing temperature. Fractography of the test bars reveals that the majority failed due to surface and edge flaws with few failures due to volume type flaws. This indicates that the powder metallurgical methods employed to produce these samples is mature.     

pH control of a fed batch reactor with precipitation

In this paper, the problem of controlling the pH, in a fed batch reactor where precipitation occurs, is considered. Due to the batch nature of the production and the effects of precipitation, the control problem is rather different from the well studied cases of continuous processes, which are usually considered under the assumption of perfect solubility. To fulfill this objective on a presented laboratory reactor used to produce precipitates, a simple control strategy is proposed, which is consistent with the limitations of the apparatus. Interestingly, the reagents under consideration have well known specifications. This point is advantageously taken into account to identify a single-input–single-output model off-line. Then, based on the obtained time-varying equation, pH set point tracking is achieved by imposing linear asymptotically stable dynamics on the amount of strong acid used for neutralization. Finally, simple rules are proposed to deal with precipitation. Representative experimental results obtained on the reactor are presented to prove the relevance of the approach.     

Electrical contact resistance between stainless steel bipolar plate and carbon felt in PEFC: A comprehensive study

Bipolar plate represents a key component of Proton Exchange Membrane Fuel Cell (PEFC) with several essential functions, among them the electric connection of elementary cells. Usually made of graphite, this component is studied worldwide in order to develop a commercially viable alternative: different ways have been being investigated, and to date, despite corrosion issues, stainless steel (SS) appears as a good candidate material, but its Electrical Contact Resistance (ECR) can reach unacceptable values when exposed to PEFC environment. This paper offers a comprehensive study of the parameters acting on ECR when using uncoated SS in PEFC: roughness, which influences the surface contact area with carbon baking, bulk composition of the alloy, which influences only partly the nature of passive films, and the composition and structure of passive films, strongly modified by surface treatments and ageing conditions.     

Microstructure–function relationships of heat-induced gels of porcine haemoglobin

The purpose of this work was to use image analysis to study the microstructural properties of haemoglobin gels, with structural changes induced by pH conditions, and their correlations with physical properties such as texture and water holding capacity (WHC). Two types of networks showing great differences in the dimensions of the gel structure were obtained as influenced by pH. At pH < 5.5 there was a shift from an aggregated to a fine-stranded gel type. Fractal dimension values revealed that more complex structures corresponded to softest and non-exudative gels. Lacunarity and pore size, which were used to study the pore distribution within the network, confirmed that softest gels with high WHC showed large number of small cavities. Finally, correlations between textural attributes, i.e. springiness and adhesiveness, and spatial variability, referred quantitatively to the degree of compactness, were also established.     

Experimental investigation of tack coat fatigue performance: Towards an improved lifetime assessment of pavement structure interfaces

This paper focuses on investigating the bonding fatigue performance between two asphalt concrete (AC) layers. For purposes of this experimental campaign, a customised double shear testing device was designed. Two interface conditions have been analysed herein: with and without a tack coat. Moreover, the corresponding fatigue behaviour has been analysed at two temperatures: 10 °C and 20 °C. As expected, the absence of a tack coat leads to a decrease in bonding fatigue performance. Since fatigue tests are highly time-consuming, a method that allows predicting the conventional interface fatigue law from accelerated shear fatigue tests has been proposed. Other novel findings on interface fatigue behaviour will also be discussed. In addition to these fatigue results, an interface failure model is proposed to evaluate the interface lifetime. Incorporating interface fatigue performance into pavement analysis proves to be a key parameter in describing in situ pavement conditions and assessing pavement durability.     

Dynamic formation of SEBS copolymer submicrometric structures

Highly ordered A-B-A block copolymer arrangements in the submicrometric scale, resulting from dewetting and solvent evaporation of thin films, have inspired a variety of new applications in the nanometric world. Despite the progress observed in the control of such structures, the intricate scientific phenomena related to regular patterns formation are still not completely elucidated. SEBS is a standard example of a triblock copolymer that forms spontaneously impressive pattern arrangements. From macroscopic thin liquid films of SEBS solution, several physical effects and phenomena act synergistically to achieve well-arranged patterns of stripes and/or droplets. That is, concomitant with dewetting, solvent evaporation, and Marangoni effect, Rayleigh instability and phase separation also play important role in the pattern formation. These two last effects are difficult to be followed experimentally in the nanoscale, which render difficulties to the comprehension of the whole phenomenon. In this paper, we use computational methods for image analysis, which provide quantitative morphometric data of the patterns, specifically comprising stripes fragmentation into droplets. With the help of these computational techniques, we developed an explanation for the final part of the pattern formation, i.e. structural dynamics related to the stripes fragmentation.