Christina Nielsen

Creativity, cooperation and interactive design

This paper focuses on ways and means of stimulating idea generation in collaborative situations involving designers, engineers, software developers, users and usability people. Particularly, we investigate tools of design, i.e. tools used in design to get ideas for a new interactive application and its use. Based on different studies from a research project that we have been involved with over the past three years, we present specific examples of such tools and discuss how they inform design. We frame this discussion through the following (theoretical) considerations: a concern for the past and the present in informing design, for using theory as a source of inspiration in design and for making extremes and multiple voices play a role in innovation. These considerations are used to structure and discuss the examples, illustrating how it is important for such tools to be concrete, tangible and even caricatured.

An analytical study of the Q(s,S) policy applied to the joint replenishment problem

Abstract We evaluate the performance of a joint replenishment inventory control policy, called the Q ( s , S ) policy, which was first suggested and characterized by Viswanathan [Manage. Sci. 43 (1997) 1447]. We argue why joint replenishment problems can be seen as one product, multiple location problems, and hence why they should be considered supply chain management problems. The paper uses Markov decision theory to work out an analytical solution procedure to evaluate the costs of a particular Q ( s , S ) policy, and thereby a method for computing the optimal Q ( s , S ) policy, under the assumption that demands follow a Poisson process. For a fixed order size Q , the problem can be decomposed for each item to find an optimal ( s , S ) policy with a stochastic review period. These subproblems can be solved by the algorithm of Zheng and Federgruen [Oper. Res. 39 (4) (1991) 654]. Thereafter it remains to find the optimal value of Q , which is done by systematic search over all relevant values of Q . The performance of the Q ( s , S ) policy is compared with the performance of other known joint ordering policies as in Pantumsinchai [Decis. Sci. 23 (1992) 111] and Viswanathan [Manage. Sci. 43 (1997) 1447]. It is shown that the Q ( s , S ) performs best among the considered policies.

Supporting Local Mobility in Healthcare by Application Roaming Among Heterogeneous Devices

This paper presents results from a research project aiming at developing an architecture supporting local mobility within hospitals. The architecture is based on fieldwork and design workshops within a large Danish hospital and it has been implemented and evaluated after a pilot phase. Our fieldwork has emphasised the differences between remote mobility, where users travel over long distances, and local mobility, where users walk around within a fixed set of buildings and/or places. Based on our field studies and our design work, we conclude that local mobility puts up three requirements for computer support; (i) it should integrate into the existing infrastructure, (ii) it should support the use of various heterogeneous devices, and (iii) it should enable seamless application roaming between these devices. The paper describes how these requirements were realized in an architecture for local mobility, and how this architecture was implemented in the healthcare domain.

Using digital cultural probes in design with children

The poster presents digital cultural probes as a way of advising the design of childrens technology.

Testing in the field

It is widely acknowledged in the HCI community that much can be gained from bringing aspects from the field into the lab, and this principle is dominating within usability groups in Danish Industry. The paper describes three such Danish usability groups and their experiments with turning the tables by using aspects from the lab in the methods applied in the field during field work projects. The context of use plays an important role for a richer understanding of the usability of particular products. As such, implications of this is not surprising, neither theoretically nor empirically. What is interesting, however, is how findings of this type are instantiated in the particular cases; how the three usability groups have used the lab approaches to aid them in working in the field and how the new methods may enhance their existing methodological toolkit. The message of the paper is that there are a variety of ways in which the theoretically driven, pre-planned, and predirected may meet the situated and open minded, both when usability work is conducted in the field and in the lab.

Augmented reality as a design tool for mobile interfaces

This paper challenges user interface paradigms for mobile devices, by using the technical classification of augmented reality interfaces as a thinking tool to develop ideas for interaction with mobile devices. The paper presents future work scenarios from a wastewater treatment plant embodying PDA applications derived from the classification of augmented reality interfaces. The focus on physical interaction with objects of work and with the mobile device provides us with a range of interaction styles, based on e.g. gestures and manipulation of objects. Furthermore, issues of transparency and directness are addressed. The future scenarios indicate that the concepts of augmented reality support solving context problems in mobile design.

Technology for boundaries

This paper presents a study of an organisation, which is undergoing a process transforming organisational and technological boundaries. In particular, we shall look at three kinds of boundaries: the work to maintain and change the boundary between the organisation and its customers; boundaries between competencies within the organisation; and boundaries between various physical locations of work, in particular between what is done in the office and what is done on site. Maintaining and changing boundaries are the processes through which a particular community sustains its identity and practice on the one hand, and where it is confronted with the identity and practices on the other.The organisation being studied employs a multitude of IT systems that support and maintain these boundaries in a particular manner that are in many ways inappropriate to the current needs of the organisation.After analysing the history and the current boundary work, the paper will propose new technological support for boundary work. In particular the paper will suggest means of supporting boundaries when these are productive and for changing boundaries when this seems more appropriate. In total, flexible technologies seem a core issue when dealing with technology for boundaries.

Enhancing the antibacterial efficacy of isoeugenol by emulsion encapsulation

Food spoilage and foodborne illnesses are two global challenges for food manufacturers. Essential oils are natural antibacterials that could have a potential for use in food preservation. Unfortunately high concentrations are needed to obtain the desired antibacterial effect, and this limits their use in food due to their adverse organoleptic properties. Encapsulation could make essential oils more effective by concentrating them in the aqueous phase of the food matrix where the bacteria are present. Here we tested encapsulation of the essential oil isoeugenol in spray-dried emulsions as a means of making isoeugenol a more effective antibacterial for use in food preservation. We used β-lactoglobulin and n-OSA starch as emulsifiers, and some emulsions were coated with positively charged chitosan to promote the contact with bacteria through electrostatic interactions. The antibacterial efficacy was quantified as the minimal bactericidal concentration in growth media, milk and carrot juice. The emulsion encapsulation system developed in this study provided high loading capacities, and encapsulation enhanced the efficacy of isoeugenol against Gram-positive and -negative bacteria in media and carrot juice but not in milk. Chitosan-coating did not enhance the efficacy further, possibly due to the aggregation of the chitosan-coated emulsions. The encapsulation system is easy to upscale and should be applicable for encapsulation of similar essential oils. Therefore, we believe it has potential to be used for natural food preservation.

Antimicrobial effect of emulsion-encapsulated isoeugenol against biofilms of food pathogens and spoilage bacteria

Food-related biofilms can cause food-borne illnesses and spoilage, both of which are problems on a global level. Essential oils are compounds derived from plant material that have a potential to be used in natural food preservation in the future since they are natural antimicrobials. Bacterial biofilms are particularly resilient towards biocides, and preservatives that effectively eradicate biofilms are therefore needed. In this study, we test the antibacterial properties of emulsion-encapsulated and unencapsulated isoeugenol against biofilms of Lis. monocytogenes, S. aureus, P. fluorescens and Leu. mesenteroides in tryptic soy broth and carrot juice. We show that emulsion encapsulation enhances the antimicrobial properties of isoeugenol against biofilms in media but not in carrot juice. Some of the isoeugenol emulsions were coated with chitosan, and treatment of biofilms with these emulsions disrupted the biofilm structure. Furthermore, we show that addition of the surfactant Tween 80, which is commonly used to disperse oils in food, hampers the antibacterial properties of isoeugenol. This finding highlights that common food additives, such as surfactants, may have an adverse effect on the antibacterial activity of preservatives. Isoeugenol is a promising candidate as a future food preservative because it works almost equally well against planktonic bacteria and biofilms. Emulsion encapsulation has potential benefits for the efficacy of isoeugenol, but the effect of encapsulation depends on the properties of food matrix in which isoeugenol is to be applied.

Effects of Tween 80 on Growth and Biofilm Formation in Laboratory Media

Tween 80 is a widely used non-ionic emulsifier that is added to cosmetics, pharmaceuticals, and foods. Because of its widespread use we need to understand how it affects bacteria on our skin, in our gut, and in food products. The aim of this study is to investigate how Tween 80 affects the growth and antimicrobial susceptibility of Staphylococcus aureus, Listeria monocytogenes, and Pseudomonas fluorescens, which are common causes of spoilage and foodborne illnesses. Addition of 0.1% Tween 80 to laboratory growth media increased the growth rate of planktonic S. aureus batch cultures, and it also increased the total biomass when S. aureus was grown as biofilms. In contrast, Tween 80 had no effect on batch cultures of L. monocytogenes, it slowed the growth rate of P. fluorescens, and it led to formation of less biofilm by both L. monocytogenes and P. fluorescens. Furthermore, Tween 80 lowered the antibacterial efficacy of two hydrophobic antimicrobials: rifampicin and the essential oil isoeugenol. Our findings underline the importance of documenting indirect effects of emulsifiers when studying the efficacy of hydrophobic antimicrobials that are dispersed in solution by emulsification, or when antimicrobials are applied in food matrixes that include emulsifiers. Furthermore, the species-specific effects on microbial growth suggests that Tween 80 in cosmetics and food products could affect the composition of skin and gut microbiota, and the effect of emulsifiers on the human microbiome should therefore be explored to uncover potential health effects.