Optical properties of infrared transmitting materials

The choice of appropriate infrared transmitting materials for high-power laser applications necessitates a knowledge of various optical parameters. Because experimental data is often scant or unreliable in frequency regions of interest it has become important to be able to predict optical parameters from either theoretical or phenomenological models. This requires identification of the major physical mechanisms, and translation of this information into a useful model. Considerable progress has been made recently, especially with regard to the frequency dependence of refraction, absorption α and photoelasticity. It has been found, for example, that frequency dispersion is important at 10.6μm for all three of the latter quantities in most alkali-halides. For most semiconductors, on the other hand, only the effects on α are significant. It is shown that the mix of existing experimental data with recent theory is now providing us, for the first time, with a fairly comprehensive view of the magnitude, frequency dependence, and temperature dependence of optical parameters of infrared transmitting materials.     

Influence of bunch maturation and chemical precursors on acrylamide formation in starchy banana chips

The present study investigated the effect of ripening stages and chemical precursors on acrylamide formation in deep-fried chips of five plantains and one cooking banana. The highest level of acrylamide was found in the cooking banana, followed by False Horn plantain and French plantain, respectively. French plantain hybrids exhibited a significantly lower (P < 0.05) level of acrylamide when compared to French plantain. The ripening stage demonstrated a positive Pearson correlation (P < 0.05, r = 0.57) with acrylamide formation. As ripening progressed, the levels of glucose and fructose significantly increased (P < 0.05) and showed a positive correlation with acrylamide formation (r = 0.85 and 0.96, respectively). The level of the amino acid asparagine during ripening was not correlated with acrylamide formation. In contrast, the level of histidine, arginine, iso-leucine and cystine during ripening was positively correlated (P < 0.05, r > 0.60) with acrylamide formation in fried chips. The higher level of TP was significantly related (P < 0.05) to the lower level of acrylamide (r = −0.62). The reduced levels of carotenoid isomers, except lutein, during fruit ripening were positively correlated (P < 0.05) with acrylamide formation, especially trans-BC (r = 0.72) and 9-cis-BC(r = 0.64).     

Processing, Physicochemical, Nutritional, and Organoleptical Properties of Dackere, an African Cereal/Tuber Food Semolina

Dackere is a granulated food made from tubers or cereals flours by women in rural areas of Northern Cameroon. The processing of the semolina faces some constraints that affect the quality and hence the potential to improve the incomes of producers. The objectives of this work were to identify and characterize the processing steps involved in the production of dackere and evaluate the physicochemical and hedonic characteristics of this food. Four groups of farmers consisting of organized and specialized women in dackere processing were used for this purpose and then followed up in their production site. The results obtained revealed that dackere was manufactured from either tubers or cereals based on the available food materials: sweet potato, cassava, corn, millet, fonio, and mixture of sweet potato/corn. Generally, the processes involved included hydrating the flour with water, granulating manually, steam cooking, and eventually drying. All these processes were done in a non-replicable manner using traditional equipment. The physicochemical characterization revealed that dackeres were in general rich in starch (60.63 to 94.99 g/100 g) and poor in proteins (0.77 to 4.42 g/100 g). Digestible starch varied from 34.9 g/100 g for corn dackere to 66.6 g/100 g for cassava and sweet potatoes dackeres, and the index of whiteness varied from 58.8 for sweet potatoes dackere to 75.8 for cassava and corn dackeres. Significant variations were observed among producers. Consumers more appreciated the sweet potato/corn dackere mixture which was associated by principal component analysis to high swallowing ability, taste, and adherence in mouth. However, they were irregular in size and brown in color, characteristics negatively correlated to acceptability.     

UF resin efficiency of MDF as affected by resin content loss, coverage level and pre-cure

A full-factorial experimental design was used to investigate the effects of three factors on UF resin efficiency. Within the limits of this study, the three factors, namely, resin content loss, resin coverage level and resin pre-cure time for mechanical blended MDF fibres were found to have significant effects on resin efficiency as evaluated by the internal bond strength (IB) of the panels. The most significant factor was resin content loss followed by resin coverage level and resin pre-cure. The resin coverage level had a positive effect on resin efficiency, while the resin content loss, resin pre-cure time at 40 °C conditions, the interactions of resin coverage level and resin content loss as well as resin coverage level with pre-cure had negative effects on resin efficiency. For a given resin content, the resin efficiency could be increased by 35% by increasing the level of resin coverage. The resin efficiency obviously decreased with resin content loss and pre-cure time.

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Beeinflussung der UF-Harzwirksamkeit bei MDF durch Harzverlust, Harzverteilungsgrad und Harzvorhärtung

Zusammenfassung In einem vollständig faktoriell angelegten Versuch wurde die Wirkung der drei Faktoren Harzverlust, Harzverteilungsgrad und Harzvorhärtung auf die UF-Harzwirksamkeit untersucht. Im Rahmen dieser Studie zeigte sich anhand der Bewertung der Querzugfestigkeit (IB) der Platten, dass sich diese drei Faktoren erheblich auf die Harzwirksamkeit bei mechanisch durchmischten MDF-Fasern auswirken. Der bedeutendste Faktor war Harzverlust gefolgt von Harzverteilungsgrad und Harzvorhärtung. Der Harzverteilungsgrad wirkte sich auf die Harzwirksamkeit positiv aus. Dagegen wirkten sich Harzverlust, Harzvorhärtungszeit bei einer Temperatur von 40 °C, sowie die gemischten Glieder aus Harzverteilungsgrad und Harzverlust sowie aus Harzverteilungsgrad und Vorhärtung negativ auf die Harzwirksamkeit aus. Durch eine verbesserte Harzverteilung konnte die Harzwirksamkeit bei gegebenem Harzgehalt um 35% erhöht werden. Die Harzwirksamkeit nimmt offensichtlich mit zunehmendem Harzverlust und Vorhärtungszeit ab.

     

Nutrient database improvement project: The influence of U.S.D.A. Quality and Yield Grade on the separable components and proximate composition of raw and cooked retail cuts from the beef rib and plate

Beef nutrition is important to the worldwide beef industry. The objective of this study was to analyze proximate composition of eight beef rib and plate cuts to update the USDA National Nutrient Database for Standard Reference (SR). Furthermore, this study aimed to determine the influence of USDA Quality Grade on the separable components and proximate composition of the examined retail cuts. Carcasses (n = 72) representing a composite of Yield Grade, Quality Grade, gender and genetic type were identified from six regions across the U.S. Beef plates and ribs (IMPS #109 and 121C and D) were collected from the selected carcasses and shipped to three university meat laboratories for storage, retail fabrication, cooking, and dissection and analysis of proximate composition. These data provide updated information regarding the nutrient content of beef and emphasize the influence of common classification systems (Yield Grade and Quality Grade) on the separable components, cooking yield, and proximate composition of retail beef cuts.     

Survival of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes on Inoculated Almonds and Pistachios Stored at -19, 4, and 24° C

The survival of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes was determined on almonds and pistachios held at typical storage temperatures. Almond kernels and inshell pistachios were inoculated with four- to six-strain cocktails of nalidixic acid-resistant Salmonella, E. coli O157:H7, or L. monocytogenes at 6 log CFU/g and then dried for 72 h. After drying, inoculated nuts were stored at -19, 4, or 24°C for up to 12 months. During the initial drying period after inoculation, levels of all pathogens declined by 1 to -log CFU/g on both almonds and pistachios. During storage, moisture content (4.8%) and water activity (0.4) of the almonds and pistachios were consistent at -19°C; increased slowly to 6% and 0.6, respectively, at 4°C; and fluctuated from 4 to 5% and 0.3 to 0.5 at 24°C, respectively. Every 1 or 2 months, levels of each pathogen were enumerated by plating; samples were enriched when levels fell below the limit of detection. No reduction in population level was observed at -19 or 4°C for either pathogen, with the exception of E. coli O157:H7-inoculated almonds stored at 4°C (decline of 0.09 log CFU/g/month). At 24°C, initial rates of decline were 0.20, 0.60, and 0.71 log CFU/g/month on almonds and 0.15, 0.35, and 0.86 log CFU/g/month on pistachios for Salmonella, E. coli O157:H7, and L. monocytogenes, respectively, but distinct tailing of the survival curves was noted for both E. coli O157:H7 and L. monocytogenes.     

Novel CaO-SiO2 sorbent and bifunctional Ni/Co-CaO/SiO2 complex for selective H2 synthesis from cellulose

Catalysis- and sorption-enhanced biomass gasification is a promising route to high-purity hydrogen (H(2)); however, most CaO-based sorbents for CO(2) capture have poor surface area and mechanical properties, lose carrying capacity over multiple uses, and have insufficient porosity to accommodate extra catalyst sites. We aimed to develop a high-surface-area CaO-SiO(2) framework onto which catalysts could be grafted. The best CaO-SiO(2) sorbent (n(Ca)/n(Si) = 2:1) maintained a CaO conversion of 65% even after 50 carbonation-decarbonation cycles, better than commercial micrometer-sized CaO or tailored CaO, because of stabilization via Ca-O-Si interactions and an ordered porous structure. Bimetallic catalyst grains (Ni/Co alloy, <20 nm) could be evenly loaded onto this structure by impregnation. The resulting bifunctional complex produced H(2) at nearly the same rate as a mixture of catalyst and commercial CaO while using less total sorbent/catalyst. Furthermore, this complex was much more durable due to its higher coking resistance and stable structure. After 25 carbonation-decarbonation cycles, the new catalyst-sorbent complex enhanced the H(2) yield from cellulose far more than a mixture of catalyst and commercial CaO did following the same treatment.