Recovery from work shifts: How long does it take?

Although regulations on work hours usually include a minimum weekly rest period, there is little empirical evidence concerning recovery from work. Shift-working nurses (N?=?61) used a handheld computer for 28 days to complete self-ratings, cognitive-performance tasks, and a sleep diary. Many measures were worse on rest days that followed a night shift rather than a day shift and tended to be worse on 1st rest days compared with subsequent rest days. Alertness was lowest on the 1st rest day following a night shift. Social satisfaction was better on workdays that were preceded by 2 rather than 1 rest day. Reaction time (RT) decreased over consecutive night shifts and tended to increase over rest days following night shifts. The results are interpreted as being consistent with the combined adaptive costs of fatigue and adjustment to and from a nocturnal routine. The practical implications for scheduling rest days are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structural and kinetic studies on ligand binding in wild-type and active-site mutants of penicillin acylase

Penicillin acylase catalyses the condensation of Calpha-substituted phenylacetic acids with beta-lactam nucleophiles, producing semi-synthetic beta-lactam antibiotics. For efficient synthesis a low affinity for phenylacetic acid and a high affinity for Calpha-substituted phenylacetic acid derivatives is desirable. We made three active site mutants, alphaF146Y, betaF24A and alphaF146Y/betaF24A, which all had a 2- to 10-fold higher affinity for Calpha-substituted compounds than wild-type enzyme. In addition, betaF24A had a 20-fold reduced affinity for phenylacetic acid. The molecular basis of the improved properties was investigated by X-ray crystallography. These studies showed that the higher affinity of alphaF146Y for (R)-alpha-methylphenylacetic acid can be explained by van der Waals interactions between alphaY146:OH and the Calpha-substituent. The betaF24A mutation causes an opening of the phenylacetic acid binding site. Only (R)-alpha-methylphenylacetic acid, but not phenylacetic acid, induces a conformation with the ligand tightly bound, explaining the weak binding of phenylacetic acid. A comparison of the betaF24A structure with other open conformations of penicillin acylase showed that betaF24 has a fixed position, whereas alphaF146 acts as a flexible lid on the binding site and reorients its position to achieve optimal substrate binding.     

Investigation of Origin of Attached Cu-Ag Droplets to Solid Particles During High-Temperature Slag/Copper/Spinel Interactions

Metallurgical and Materials Transactions B - This study investigates the origin of mechanically entrained metal droplets in liquid slag due to their interaction with solid spinel particles. Two...     

Life cycle assessment of Jatropha biodiesel as transportation fuel in rural India

Since 2003 India has been actively promoting the cultivation of Jatropha on unproductive and degraded lands (wastelands) for the production of biodiesel suitable as transportation fuel. In this paper the life cycle energy balance, global warming potential, acidification potential, eutrophication potential and land use impact on ecosystem quality is evaluated for a small scale, low-input Jatropha biodiesel system established on wasteland in rural India. In addition to the life cycle assessment of the case at hand, the environmental performance of the same system expanded with a biogas installation digesting seed cake was quantified. The environmental impacts were compared to the life cycle impacts of a fossil fuel reference system delivering the same amount of products and functions as the Jatropha biodiesel system under research. The results show that the production and use of Jatropha biodiesel triggers an 82% decrease in non-renewable energy requirement (Net Energy Ratio, NER = 1.85) and a 55% reduction in global warming potential (GWP) compared to the reference fossil-fuel based system. However, there is an increase in acidification (49%) and eutrophication (430%) from the Jatropha system relative to the reference case. Although adding biogas production to the system boosts the energy efficiency of the system (NER = 3.40), the GWP reduction would not increase (51%) due to additional CH₄ emissions. For the land use impact, Jatropha improved the structural ecosystem quality when planted on wasteland, but reduced the functional ecosystem quality. Fertilizer application (mainly N) is an important contributor to most negative impact categories. Optimizing fertilization, agronomic practices and genetics are the major system improvement options.     

Transport of Dissolved Si from Soil to River: A Conceptual Mechanistic Model

This paper reviews the processes which determine the concentrations of dissolved silicon (DSi) in soil water and proposes a conceptual mechanistic model for understanding the transport of Si through soils to rivers. The net DSi present in natural waters originates from the dissolution of mineral and amorphous Si sources in the soil, as well as precipitation processes. Important controlling factors are soil composition (mineralogy and saturated porosity) and soil water chemistry (pH, concentrations of organic acids, CO₂ and electrolytes). Together with production, polymerization and adsorption equations they constitute a mechanistic framework determining DSi concentrations. We discuss how key controls differ across soil horizons and how this can influence the DSi transport. A typical podzol soil profile in a temperate climate is used as an example, but the proposed model is transferrable to other soil types. Additionally, the impact of external forcing factors such as seasonal climatic variations and land use is evaluated. This blueprint for an integrated model is a first step to mechanistic modelling of Si transport processes in soils. Future implementation with numerical methods should validate the model with field measurements.     

Designing a cost-effective CO2 storage infrastructure using a GIS based linear optimization energy model

Large-scale deployment of carbon capture and storage needs a dedicated infrastructure. Planning and designing of this infrastructure require incorporation of both temporal and spatial aspects. In this study, a toolbox has been developed that integrates ArcGIS, a geographical information system with spatial and routing functions, and MARKAL, an energy bottom-up model based on linear optimization. Application of this toolbox led to blueprints of a CO₂ infrastructure in the Netherlands. The results show that in a scenario with 20% and 50% CO₂ emissions reduction targets compared to their 1990 level in respectively 2020 and 2050, an infrastructure of around 600 km of CO₂ trunklines may need to be built before 2020. Investment costs for the pipeline construction and the storage site development amount to around 720 m€ and 340 m€, respectively. The results also show the implication of policy choices such as allowing or prohibiting CO₂ storage onshore on CO₂ Capture and Storage (CCS) and infrastructure development. This paper illustrates how the ArcGIS/MARKAL-based toolbox can provide insights into a CCS infrastructure development, and support policy makers by giving concrete blueprints over time with respect to scale, pipeline trajectories, and deployment of individual storage sites.     

Insulinoma associated with liver lesions: value of MR imaging

We report on a middle-aged woman who presented with clinical and biochemical findings of insulinoma. Preoperative evaluation by ultrasound, CT, and angiography located the pancreatic lesion but also revealed two focal liver lesions. The latter were interpreted as metastases. MR imaging with injection of superparamagnetic iron oxide particles not only localized the insulinoma but proved to be the only noninvasive technique capable to exclude presence of liver metastases preoperatively. This reversed management to minimal laparoscopic surgery. Recent literature of preoperative imaging evaluation of insulinoma and focal liver lesions is discussed.     

Legumin allergens from peanuts and soybeans: effects of denaturation and aggregation on allergenicity

Legumin proteins Ara h 3 from peanuts and glycinin from soybeans are increasingly described as important allergens. The stability of an allergen's IgE binding capacity towards heating and digestion is considered an important characteristic for food allergens. We investigated the effects of heating and digestion on the IgE binding of Ara h 3 and glycinin. Both proteins are relatively stable to denaturation, having denaturation temperatures ranging from 70 to 92 degrees C, depending on their quaternary structure and the ionic strength. Aggregates were formed upon heating, which were partly soluble for glycinin. Heating slightly decreased the pepsin digestion rate of both allergens. However, heating did not affect the IgE binding capacity of the hydrolyzates, as after only 10 min of hydrolysis no IgE binding could be detected any more in all samples. Peanut allergen Ara h 1, when digested under equal conditions, still showed IgE binding after 2 h of hydrolysis. Our results indicate that the IgE binding capacity of legumin allergens from peanuts and soybeans does not withstand peptic digestion. Consequently, these allergens are likely unable to sensitize via the gastro-intestinal tract and cause systemic food allergy symptoms. These proteins might thus be less important allergens than was previously assumed.     

Heat denaturation of Brazil nut allergen Ber e 1 in relation to food processing

Ber e 1, a major allergen from Brazil nuts, is very stable to in vitro peptic digestion. As heat-induced denaturation may affect protein digestibility, the denaturation behaviour of Ber e 1 was investigated. The denaturation temperature of Ber e 1 varies from approximately 80–110 °C, depending on the pH. Upon heating above its denaturation temperature at pH 7.0, the protein partly forms insoluble aggregates and partly dissociates into its polypeptides, whereas heating at pH 5.0 does neither induce aggregation, nor dissociation of the protein. The denaturation temperature of approximately 110 °C at pH values corresponding to the general pH values of foods (pH 5–7) is very high and is expected to be even higher in Brazil nuts themselves. As a result, it is unlikely that heat processing causes the denaturation of all Ber e 1 present in food products. Consequently, the allergen is assumed to be consumed (mainly) in its native form, having a high stability towards pepsin digestion.     

Oxidative stability of mahi mahi red muscle dipped in tilapia protein hydrolysates

The oxidative stability of mahi mahi red muscle dipped in tilapia protein hydrolysates was evaluated. Alkali solubilised tilapia protein isolate was hydrolysed using Flavourzyme to 13% degree of hydrolysis. Whole tilapia protein hydrolysate and ultrafiltered fraction <10 kDa were used as dip solutions. Mahi mahi red muscle was dip treated either for 2 or 4 min and stored at 4 °C. Lipid hydroperoxides (PV), thiobarbituric acid reactive substances (TBARS) and a∗ value were measured at regular intervals. Results showed that dip treatments significantly decreased (p < 0.05) the formation of PV and TBARS over 90 h storage time. There was no significant (p > 0.05) difference between WH and <10 kDa fractions, and between 2 and 4 min treatments. Red colour of treated samples measured as a∗ value decreased with storage time, but was not significantly different from the control. It could be concluded that dip treatment for 2 min in whole tilapia protein hydrolysate may be used as a potential antioxidant treatment for improving oxidative stability of fish fillets.