Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H₂ kg⁻¹ VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min⁻¹ successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H₂ kg⁻¹ VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.     

Pure hydrogen co-production by membrane technology in an IGCC power plant with carbon capture

The CO₂ capture in Integrated Gasification Combined Cycle (IGCC) plants causes a significant increase of the cost of electricity (COE) and thus determines high CO₂ mitigation cost (cost per ton of avoided CO₂ emissions). In this work the economic sustainability of the co-production of pure hydrogen in addition to the electricity production was assessed by detailed process simulations and a techno-economic analysis. To produce pure hydrogen a Water Gas Shift reactor and a Selexol^® process was combined with H₂ selective palladium membranes. This innovative process section was compared with the more conventional Pressure Swing Adsorption in order to produce amount of pure hydrogen up to 20% of the total hydrogen available in the syngas.Assuming for a base case a hydrogen selling price of 3 €/kg and a palladium membrane cost of 9200 €/m², a cost of electricity (COE) of 64 €/MWh and a mitigation cost of 20 €/ton_CO2 were obtained for 90% captured CO₂ and 10% hydrogen recovery. An increase of the hydrogen recovery up to 20% determines a reduction of the COE and of the mitigation cost to 50 €/MWh and 5 €/ton_CO2, respectively. A sensitivity analysis showed that even a 50% increase of cost of the membrane per unit surface could determine a COE increase of only about 10% and a maximum increase of the mitigation cost of further 5 €/ton_CO2.     

The effects of photic driving on mood states

The capacity to maintain vigilance generally falls with time on task. However, it has been suggested that, for example, the effects of sleep loss need a rather long time on task to become evident. The present experiment examined when significant deterioration of performance occurred in a 34-min visual vigilance task (with 32 signals) given to twelve subjects every 3 h across 64 h without sleep. Results from the whole test, the first eight signals, and even the first signal varied significantly across the experiment and were significantly lower than baseline after 24 h awake. The rate of decline over time on task was similar across the experiment. Less than half the misses could be attributed to electrophysiologically defined sleepiness. It was concluded that there is no "safe" duration of a monotonous task if the situation is undemanding and boring, but that the effect may become immediately evident. This may have practical implications in terms of safety.     

A multiagent system for retrieving bioinformatics publications from web sources

Due to the enormous amount of information available on the Internet, extracting and classifying it has become one of the most important tasks. This principle is valid also while searching for scientific publications. This paper describes a system able to retrieve scientific publications from the Web throughout a text categorization process. To this end, a generic multiagent architecture has been customized according to the requirements imposed by the specific task. Experiments have been performed on publications extracted from BMC Bioinformatics and PubMed digital archives.     

Silk fibroin/cellulose blend films: Preparation,structure, and physical properties

This article deals with the preparation and characterization of silk fibroin (Bombyx mori)/cellulose blend films. Following dissolution with a metal complex solution, the average molecular weight of silk fibroin slightly decreased. While cellulose was almost unaffected. After coagulation and washing, transparent films were obtained by blending fibroin and cellulose in all proportions. The crystalline structures of regenerated fibroin and cellulose were β-form and cellulose II, respectively, as shown by the characteristic x-ray diffraction profiles. Density values increased with cellulose content, though less than expected from a pure additive behavior. Moisture regain increased following the addition of a small amount of cellulose to silk fibroin. The mechanical properties showed that both strength and elongation at break of silk fibroin films were improved by blending with cellulose. IR spectra exhibited changes in the skeletal frequences of silk fibroin, suggesting the occurrence of intermolecular interactions between fibroin and cellulose through hydrogen bond formation. © 1995 John Wiley & Sons, Inc.     

The solid-state rearrangement of the Wells-Dawson K6P2W18O62·10H2O to a stable Keggin-type heteropolyanion phase: a catalyst for the selective oxidation of isobutane to isobutene

The thermal and structural stability of the Wells-Dawson-type heteropoly compound K₆P₂W₁₈O₆₂·10H₂O was examined by FT-IR spectroscopy, X-ray powder diffraction, thermogravimetric analysis and HRTEM. It was found that calcination at temperatures higher than 850 K led to the formation of a Keggin-type compound K₃PW₁₂O₄₀, containing small amounts of an additional phase originated from the high-temperature interaction between potassium phosphate (K₃PO₄ formed during the decomposition of the K₆P₂W₁₈O₆₂·10H₂O) and the Keggin-type compound itself. The Keggin-type product showed a higher activity in the selective oxidative dehydrogenation of isobutane to isobutene compared to both the Wells-Dawson precursor and to pure, authentic K₃PW₁₂O₄₀. This higher activity can be tentatively attributed to the presence of an amorphous layer of unknown stoichiometry at the surface of the thermally rearranged Wells-Dawson compound.     

Lymphocyte subpopulations of workers in a plant producing plastic materials (preliminary study)

Lymphocyte subpopulations were studied in 31 men working in a plant producing plastic materials in relation with control groups of similar age and smoking habit. 8 workers (group A) were exposed to solvents (mainly methylethylketone and dimethylformamide), 8 men (group B) to dust containing particles of calcium carbonate, polyvinylchloride, phtalates, unsaturated oils, paraffin wax, iron oxides, titanium bioxides, barium, zinc and lead and 15 men (group C), working in the same department as group B, were studied after a period of 16 months during which lead chromate was employed in the preparation of colors. The lymphocyte subpopulations were normal in group A, while in B there was a significant increase of HLA-DR + cells (monocytes, B and activated T lymphocytes). In group C, T helper/inducer lymphocytes (mainly CD4(+)-CD45RO- "virgin" lymphocytes), CD19+ B lymphocytes, CD3-HLADR+ and CD3-CD25+ (activated B lymphocytes and monocytes) were significantly reduced without changes of serum IgM, IgG and IgA. Highly significant correlation was found between B lymphocytes (reduced in the workers about 40%) and CD4(+)-CD45R0+ "memory" lymphocytes (reduced about 20%). Moreover, blood lead (correlated with urinary chromium) showed a highly significant negative correlation with the B lymphocytes. This study demonstrates that combined exposure to toxic agents produces specific modifications in the lymphocyte subsets without changes in immunoglobulins and confirms the results of previous researches showing that the exposure to lead or chromate induces reduction of lymphocytes in the peripheral blood.     

A simulated insect diet as a water source for quail: effects on body mass and reproduction

Compared with control birds receiving ad libitum free-water, the total water intake of male and female northern bobwhite declined when only mealworms were available as a source of water. Male northern bobwhite sustained tissue mass and reproductive function with mealworms as their only source of water. Female northern bobwhite could not sustain body, ovary, and oviduct mass, and rate of egg production with mealworms as their only source of water. We suggest that, without free-water, breeding females require a diet with a water:dry matter ratio of greater than 1:1.29 (> 44% water).     

Learning organisation and human resources management practices: an exploratory research in medium-sized enterprises undergoing a lean implementation

Despite the fact that Lean Manufacturing (LM) implementation has been widely discussed in the literature, a reduced number of works focus on medium-sized enterprises (MEs). Such gap becomes more evident when searching for works exploring the dimensions of learning organisation (DLO) that surround LM implementation in MEs. This paper aims at assessing DLO maturity and the importance of human resources management (HRM) practices in MEs that are starting LM implementation. We verify the applicability of a method for assessing maturity levels of DLO and HRM practices in seven different MEs. The method was originally conceived for large enterprises well advanced in the lean implementation process; it combines concepts of HRM and organisational learning with lean implementation roadmaps. Adapting the method for application in MEs allows such companies to anticipate and minimise organisational learning problems by conducting appropriate HRM practices, leading to a more effective LM implementation. We conclude that the method is a suitable diagnostic tool for MEs, indicating which phases of the lean roadmap are better prepared to be implemented.