The effect of cocoa fermentation and weak organic acids on growth and ochratoxin A production by Aspergillus species

The acidic characteristics of cocoa beans have influence on flavor development in chocolate. Cocoa cotyledons are not naturally acidic, the acidity comes from organic acids produced by the fermentative microorganisms which grow during the processing of cocoa. Different concentrations of these metabolites can be produced according to the fermentation practices adopted in the farms, which could affect the growth and ochratoxin A production by fungi. This work presents two independent experiments carried out to investigate the effect of some fermentation practices on ochratoxin A production by Aspergillus carbonarius in cocoa, and the effect of weak organic acids such as acetic, lactic and citric at different pH values on growth and ochratoxin A production by A. carbonarius and Aspergillus niger in culture media. A statistical difference (ρ<0.05) in the ochratoxin A level in the cured cocoa beans was observed in some fermentation practices adopted. The laboratorial studies demonstrate the influence of organic acids on fungal growth and ochratoxin A production, with differences according to the media pH and the organic acid present. Acetic acid was the most inhibitory acid against A. carbonarius and A. niger. From the point of view of food safety, considering the amount of ochratoxin A produced, fermentation practices should be conducted towards the enhancement of acetic acid, although lactic and citric acids also have an important role in lowering the pH to improve the toxicity of acetic acid.     

A general battery model for PV system simulation

A battery model is proposed as a tool to simulate and optimize photovoltaic (PV) / storage systems. the normalized form of the equations with respect to the battery capacity allows us to generalize its use for any type and size of lead-acid batteries. The validity of this model to represent the battery voltage evolution during charge, overcharge and discharge processes and to predict the performance of solar systems under different operational conditions is analysed. Moreover, the battery efficiency losses are presented as a function of the upper regulation thresholds of the charge controllers and the size of the array and storage systems in a domestic application in the climate of Madrid.     

Experiments with micro-fin tube in single phase

This work shows heat transfer and friction characteristics for water single-phase flow in micro-fin tubes. The analysis of thermal and hydraulic behavior from a laminar to a turbulent flow was carried out in an experimental setup with a 9.52 mm diameter micro-fin tube. The tube was wrapped up with an electrical resistance tape to supply a constant heat flux to its surface. Different operational conditions were considered in the heating tests. The inlet and outlet temperatures, differential wall temperatures along the tube, pressure drop and flow rate were measured. The relationships of heat flux and flow rate with heat transfer coefficient and pressure drop were analyzed. Under the same conditions, comparative experiments with an internally smooth tube were conducted. The micro-fin tube provides higher heat transfer performance than the smooth tube (in turbulent flow h_micro-fin/h_smooth=2.9). In spite of the increase in pressure drop (Δp_micro-fin/Δp_smooth=1.7) the heat transfer results were significantly higher (about 80%). This shows the advantages of this enhanced configuration in thermal performance related to conventional tubes. The smooth tube results were validated by the comparison with the Dittus–Boelter and Gnielinski correlations. For the micro-fin tube an empirical correlation to the heat transfer coefficient adjusted from the set of measured data is proposed. The values obtained are in conformity with experimental results.     

Analysing NBTI Impact on SRAMs with Resistive Defects

Density’s increase in Static Random Access Memory (SRAM) has become an important concern for testing, since new types of defects, that may occur during the manufacturing process, are introduced. On the one hand, new manufacturing defects may lead to dynamic faults, which are considered one of the most important causes of test escape in deep-submicron technologies. On the other hand, the SRAM’s robustness is considered crucial, since it may affect the entire SoC. One of the most important phenomena to degrade SRAM reliability is Negative-Bias Temperature Instability (NBTI) causing the memory cells’ aging. In this context, the paper proposes to analyse the impact of NBTI on SRAM cells with resistive defects that eventually escape manufacturing test and, with aging, may generate faults over time. Finally, SPICE simulations adopting a commercial 65 nm CMOS technology library have been performed in order to estimate NBTI’s precise impact over time.     

Gate sizing using geometric programming

A two-step transistor sizing optimization method based on geometric programming for delay/area minimization is presented. In the first step, Elmore delay is minimized using only minimum and maximum transistor size constraints. In the second step, the minimized delay found in the previous step is used as a constraint for area minimization. In this way, our method can target simultaneously both delay and area reduction. Moreover, by relaxing the minimized delay, one may further reduce area with small delay penalty. Gate sizing may be accomplished through transistor sizing tying each transistor inside a cell to a same scale factor. This reduces the solution space, but also improves runtime as less variables are necessary. To analyze this tradeoff between execution time and solution quality a comparison between gate sizing and transistor sizing is presented. In order to qualify our approach, the ISCAS??85 benchmark circuits are mapped to a 45?nm technology using a typical standard cell library. Gate sizing and transistor sizing are performed considering delay minimization. Gate sizing is able to reduce delay in 21?%, on average, for the same area and power values of the sizing provided by standard-cells library. Then, the transistor sizing is executed and delay can be reduced in 40.4?% and power consumption in 2.9?%, on average, compared to gate sizing. However, the transistor sizing takes about 23 times longer to be computed, on average, using a number of variables twice higher than gate sizing. Gate sizing optimizing area is executed considering a delay constraint. Three delay constraints are considered, the minimum delay given by delay optimization and delay 1 and 5?% higher than minimum delay. An energy/delay gain (EDG) metric is used to quantify the most efficient tradeoff. Considering the minimum delay, area (power) is reduced in 28.2?%, on average. Relaxing delay by just 1?%, area (power) is reduced in 41.7?% and the EDG metric is 41.7. Area can be reduced in 51?%, on average, relaxing delay by 5?% and EDG metric is 10.2.     

Occurrence of ochratoxin A in cocoa by-products and determination of its reduction during chocolate manufacture

This work reports an investigation carried out to assess the natural occurrence of ochratoxin A in 168 samples from different fractions obtained during the technological processing of cocoa (shell, nibs, liquor, butter, cake and cocoa powder) and the reduction of ochratoxin A during chocolate manufacture. Ochratoxin A analyses were performed with immunoaffinity columns and detection by high performance liquid chromatography. Concerning the natural ochratoxin A contamination in cocoa by-products, the highest levels of ochratoxin A were found in the shell, cocoa powder and cocoa cake. The cocoa butter was the least contaminated, showing that ochratoxin A seems to remain in the defatted cocoa solids. Under the technological conditions applied during the manufacture of chocolate in this study and the level of contamination present in the cocoa beans, this experiment demonstrated that 93.6% of ochratoxin A present in the beans was reduced during the chocolate producing.     

Meiotic behavior and pollinic viability in bean cultivars

The aims of this study were to determine the meiotic behavior and to estimate pollen grains viability in bean (Phaseolus vulgaris L.) cultivars. Flower buds were collected during different developmental stages of the Mesoamerican bean cultivars IAPAR 44, Guapo Brilhante, BRS Expedito, BRS Valente, Guateian 6662 and Pérola, and the Andean bean cultivar Iraí, grown in a greenhouse. The meiotic index was determined by anther squashing of material fixed in absolute ethanol-glacial acetic acid (3:1) and stained with acetic orcein. No meiotic abnormalities were observed and the meiotic indices were high for all cultivars, indicating that the mismatch generated during crosses is not related to any meiotic changes. Estimation of pollen viability was made by comparing acetic orcein staining vs. Alexander’s reactive: pollen viability was high in all cultivars with either stain, but was significantly higher when using the acetic orcein stain (>99%). Though some cultivar showed a significantly smaller pollen size, the range of variation among cultivars was low (means’ range 51-66 μm)     

Flow Boiling Heat Transfer Characteristics of R600a in Multiport Minichannel

ABSTRACT

Evaporators of small and medium refrigeration systems, as in commercial and automobile air conditioning applications, are being studied to develop more compact and lighter equipment, that reaches good thermal performance and reliability, with low pressure drop. In this way, evaporators are being designed with small channels and materials like aluminum. Moreover, different refrigerants are being tested to substitute for hydrofluorocarbon (HFC) refrigerants, with different operational temperatures and pressures. Some of them, like hydrocarbons, although they present advantages with respect to their thermodynamic and transport properties, should be used with small charge in the system due to their flammability. This work presents the results of an experimental study to characterize the flow boiling of the refrigerant R600a (isobutane) in a multiport aluminum extruded tube with 7 parallel minichannels of 1.47 mm hydraulic diameter. The effects of mass velocity, heat flux, and vapor quality on heat transfer were investigated for constant saturation temperature and pressure. Heat fluxes in the range from 5 to 30 kW m^?2, mass velocities set to discrete values in the range of 50 to 200 kg m^?2 s^?1, and saturation temperature of 20°C were considered. It was verified a significant effect of heat flux. Moreover, some images of flow patterns, in different conditions, are presented, and the main patterns identified were slug, intermittent, and annular.     

Human Neural Stem Cell-Based Drug Product: Clinical and Nonclinical Characterization

Translation of cell therapies into clinical practice requires the adoption of robust production protocols in order to optimize and standardize the manufacture and cryopreservation of cells, in compliance with good manufacturing practice regulations. Between 2012 and 2020, we conducted two phase I clinical trials (EudraCT 2009-014484-39, EudraCT 2015-004855-37) on amyotrophic lateral sclerosis secondary progressive multiple sclerosis patients, respectively, treating them with human neural stem cells. Our production process of a hNSC-based medicinal product is the first to use brain tissue samples extracted from fetuses that died in spontaneous abortion or miscarriage. It consists of selection, isolation and expansion of hNSCs and ends with the final pharmaceutical formulation tailored to a specific patient, in compliance with the approved clinical protocol. The cells used in these clinical trials were analyzed in order to confirm their microbiological safety; each batch was also tested to assess identity, potency and safety through morphological and functional assays. Preclinical, clinical and in vitro nonclinical data have proved that our cells are safe and stable, and that the production process can provide a high level of reproducibility of the cultures. Here, we describe the quality control strategy for the characterization of the hNSCs used in the above-mentioned clinical trials.     

Aflatoxigenic fungi and aflatoxin in cocoa

This paper reports the occurrence of aflatoxigenic fungi and the presence of aflatoxins in 226 cocoa samples collected on Brazilian farms. The samples were taken at various stages of fermentation, drying and storage. A total of 819 potentially aflatoxigenic fungi were isolated using Dichloran 18% Glycerol agar after surface disinfection, and identified by standard techniques. The ability of the fungi to produce aflatoxins was determined using the agar plug technique and TLC. The presence of aflatoxins in cocoa samples was determined by HPLC using post-column derivatization with bromide after immunoaffinity column clean up. The aflatoxigenic fungi isolated were Aspergillus flavus, A. parasiticus and A. nomius. A considerable increase in numbers of these species was observed during drying and storage. In spite of the high prevalence of aflatoxigenic fungi, only low levels of aflatoxin were found in the cocoa samples, suggesting the existence of limiting factors to the accumulation of aflatoxins in the beans.