Cognitive task analysis of a complex work domain: a case study

Conducting an analysis of a work domain is a necessary prerequisite for making sound and effective human factors design recommendations. There are several properties of complex work domains which put very strong requirements on the type of analysis methods which can be meaningfully used. Traditional task analysis methods based on observable actions are no longer appropriate. In this paper, we describe a set of methods that we have adopted and have found to be useful in conducting a cognitive task analysis of a complex work domain. From our experience with this particular case study, we have found that it is necessary to adopt a variety of different methods to examine a particular work domain, and use the converging evidence from these several methods to attain a final, comprehensive understanding of that domain.     

Process for production of calcined phosphate in a grate furnace

Experimental results on bench scale production of calcined phosphate in a grate furnace are presented. Phosphate concentrates were mixed with silica, sodium carbonate and charcoal in varying amounts and granulated (4–6 mm), in some cases with the aid of phosphoric acid. The granules were dried and calcined at 1140–1300°C in a grate furnace. Products with 24.4 to 30.7% total P₂O₅ were obtained with solubility higher than 70% in 2% citric acid.Other experiments were done employing pelletized (4–6 mm) sugar cane bagasse as fuel instead of coal. In these cases, the raw materials silica, sodium carbonate and phosphate concentrates were granulated and then mixed with the pelletized sugar cane bagasse. Two products with 26.1 and 29.4% total P₂O₅ containing respectively 18.8 and 24.0% soluble P₂O₅ (in 2% citric acid solution) were obtained by calcination at temperatures of 930 and 1300°C respectively.The products of both experiments were mainly citric acid-soluble phosphates (rhenanite and andoite) with small amounts of non-reacted apatite.     

An Inverse Substrate Orientation for the Regioselective Acylation of 3′,5′‐Diaminonucleosides Catalyzed by Candida antarctica lipase B?

Candida antarctica lipase B (CAL-B) catalyzes the regioselective acylation of natural thymidine with oxime esters and also the regioselective acylation of an analogue, 3',5'-diamino-3',5'-dideoxythymidine with nonactivated esters. In both cases, acylation favors the less hindered 5'-position over the 3'-position by upto 80-fold. Computer modeling of phosphonate transition-state analogues for the acylation of thymidine suggests that CAL-B favors acylation of the 5'-position because this orientation allows the thymine ring to bind in a hydrophobic pocket and forms stronger key hydrogen bonds than acylation of the 3'-position. On the other hand, computer modeling of phosphonamidate analogues of the transition states for acylation of either the 3'- or 5'-amino groups in 3',5'-diamino-3',5'-dideoxythymidine shows similar orientations and hydrogen bonds and, thus, does not explain the high regioselectivity. However, computer modeling of inverse structures, in which the acyl chain binds in the nucleophile pocket and vice versa, does rationalize the observed regioselectivity. The inverse structures fit the 5'-, but not the 3'-intermediate thymine ring, into the hydrophobic pocket, and form a weak new hydrogen bond between the O-2 carbonyl atom of the thymine and the nucleophile amine only for the 5'-intermediate. A water molecule might transfer a proton from the ammonium group to the active-site histidine. As a test of this inverse orientation, we compared the acylation of thymidine and 3',5'-diamino-3',5'-dideoxythymidine with butyryl acyl donors and with isosteric methoxyacetyl acyl donors. Both acyl donors reacted at equal rates with thymidine, but the methoxyacetyl acyl donor reacted four times faster than the butyryl acyl donor with 3',5'-diamino-3',5'-dideoxythymidine. This faster rate is consistent with an inverse orientation for 3',5'-diamino-3',5'-dideoxythymidine, in which the ether oxygen atom of the methoxyacetyl group can form a similar hydrogen bond to the nucleophilic amine. This combination of modeling and experiments suggests that such lipase-catalyzed reactions of apparently close substrate analogues like alcohols and amines might follow different pathways.     

Cryopreservation of Agronomic Plant Germplasm Using Vitrification-Based Methods: An Overview of Selected Case Studies

Numerous environmental and endogenous factors affect the level of genetic diversity in natural populations. Genetic variability is the cornerstone of evolution and adaptation of species. However, currently, more and more plant species and local varieties (landraces) are on the brink of extinction due to anthropopression and climate change. Their preservation is imperative for the sake of future breeding programs. Gene banks have been created worldwide to conserve different plant species of cultural and economic importance. Many of them apply cryopreservation, a conservation method in which ultra-low temperatures (−135 °C to −196 °C) are used for long-term storage of tissue samples, with little risk of variation occurrence. Cells can be successfully cryopreserved in liquid nitrogen (LN) when the adverse effect of ice crystal formation and growth is mitigated by the removal of water and the formation of the so-called biological glass (vitrification). This state can be achieved in several ways. The involvement of key cold-regulated genes and proteins in the acquisition of cold tolerance in plant tissues may additionally improve the survival of LN-stored explants. The present review explains the importance of cryostorage in agronomy and presents an overview of the recent works accomplished with this strategy. The most widely used cryopreservation techniques, classic and modern cryoprotective agents, and some protocols applied in crops are considered to understand which parameters provide the establishment of high quality and broadly applicable cryopreservation. Attention is also focused on the issues of genetic integrity and functional genomics in plant cryobiology.     

Multi-view kernel construction

In many problem domains data may come from multiple sources (or views), such as video and audio from a camera or text on and links to a web page. These multiple views of the data are often not directly comparable to one another, and thus a principled method for their integration is warranted. In this paper we develop a new algorithm to leverage information from multiple views for unsupervised clustering by constructing a custom kernel. We generate a multipartite graph (with the number of parts given by the number of views) that induces a kernel we then use for spectral clustering. Our algorithm can be seen as a generalization of co-clustering and spectral clustering and a relative of Kernel Canonical Correlation Analysis. We demonstrate the algorithm on four data sets: an illustrative artificial data set, synthetic fMRI data, voxels from an fMRI study, and a collection of web pages. Finally, we compare its performance to common alternatives.     

Static and dynamic policies with RFID for the scheduling of retrieval and storage warehouse operations

Warehouses are essential components of logistics and supply chains. The performance of warehouse operations significantly affects the efficiency of the whole chain it belongs to. Radio frequency identification (RFID) is an emerging technology capable of providing real-time information about the location and properties of tagged object(s), such as people, equipment or products. The objective of this article is threefold, to propose and compare different offline and online policies for the scheduling of warehouse operations, to design a tool that allows the decision maker to compare policies and environments without putting them into practice, and to study the benefits that can be obtained if RFID is used in a particular type of warehouse. To this end, we have developed a stylised model that captures and generalises the main characteristics of the structure, routing and sequencing operations of a given real warehouse. The model incorporates several realistic features never or rarely discussed in the literature in the presence of RFID, for example, due dates in the orders that have to be performed and congestion in the warehouse due to the presence of multiple vehicles performing the orders. We have also developed a set of heuristic routing and sequencing procedures that take and, alternatively, do not take into account real time information, and compare their performance via simulation on a set of randomly generated, although realistic, warehouse scenarios. Computational results show the effect in terms of due data fulfilment and tardiness minimisation if the RFID technology is installed and offline and online management policies are considered.     

The effects of virtuality level on task-related collaborative behaviors: The mediating role of team trust

This study aims to analyze the mediating role of team trust in the relationship between virtuality level and task-related collaborative behaviors. Three types of task-related collaborative behaviors were studied, namely team coordination, team cooperation, and team information exchange. Drawing upon theory and research on virtual teams and trust, we hypothesized that team trust partially mediated the effects of virtuality level on team coordination, team cooperation, and team information exchange. A laboratory experiment was carried out with 65 four-person teams randomly assigned to three communication media with different virtuality levels (face-to-face, video conference and computer-mediated communication). The results showed that team trust partially mediated the relationship between virtuality level and team coordination, and fully mediated this relationship with team cooperation and team information exchange.     

Delayed Teleoperation with Force Feedback of a Humanoid Robot

Machine Intelligence Research - Teleoperation systems allow the extension of human capabilities to remote-control devices by providing the operator with conditions similar to those at the remote...