Predicting road crashes from a mathematical model of alertness regulation--The Sleep/Wake Predictor

Sleepiness is related to factors such as the time of day, the time since awakening and the duration of prior sleep. The present study investigated whether actual road crashes could be predicted from a mathematical model based on these three factors (the Sleep/Wake Predictor-SWP). Data were derived from a population-based case-control study of serious injury crashes. Data on accident time (or control sampling time) and start and end of prior sleep were entered into the model (blind). The predicted sleepiness values were used in logistic regressions. The results showed a highly significant odds ratio (OR)=1.72 (confidence interval=1.41-2.09) for each incremental step of sleepiness on the output sleepiness scale (nine steps). There was also a significant interaction with blood alcohol level, showing high OR values for high sleepiness levels and alcohol levels above 50 mg% (0.05 g/dl). It was concluded that the model is a good predictor of road crashes beyond that of alcohol level, and that interaction between the two carries a very high risk.     

Synthesis and characterization of surface-active compounds derived from cholesterol derivatives and glucose

The synthesis and characterization of surface-active compounds based on various steroid derivatives and glucose are presented. The hydrophobic and hydrophilic parts of the compounds were linked via glucosidic bonds. All compounds were found to have very low water solubility and only limited solubility in various organic solvents. The compounds were investigated according to their ability to interact with an anionic surfactant, sodium dodecylsulfate (SDS), in order to induce a decrease in the critical micelle concentration (CMC) of the surfactants. This synergistic effect was pronounced for cholestanol-6-on-β-D-glucopyranoside and for cholestan-3,6-diol-β-D-glucopyranoside. These two compounds lowered the CMC from 8 to 6 and 0.6 mM, respectively, for water solutions of SDS/glucoside with a molar ratio of 92∶8. Furthermore, the ability of the compounds to stabilize lipid membranes, in liposomes, at varying concentrations of Ca²⁺, was studied. The compounds were, as expected, found to induced stabilization similar to that of cholesterol.     

Frequency conditions for stable networked controllers with time-delay

The paper analyses a networked control system consisting of a linear time-invariant system with a static feedback nonlinearity, subject to large delays in the feedback loop. This model is valid for example in wireless data flow control, where a saturation occurs since the flow is one-directional. The present paper extends previous results by proving necessity, in case the loop gain is uniformly less than one. The results are validated and illustrated in a simulation study.     

Control of a wind farm with an internal direct current collection grid

For a high‐voltage, direct current connected wind farm, an internal direct current (DC) collection grid is a possible further development that can reduce the weight of the transformers significantly, with average losses for the DC system of 3%. For the internal DC grid, the DC/DC converters control the power flow and thereby also the voltages. In this paper, the control of the DC/DC converters in the wind farm is investigated in detail. The control strategy is presented, and suitable time constants are chosen depending on the switching frequency of the converters. Also, the required capacitor size to keep the voltage variations within 5% of the rated value in the case without communication within the wind farm is derived. It is shown that the control is stable and can handle faults on the external grid without any communication within the wind farm. Copyright © 2011 John Wiley & Sons, Ltd.     

Considerations for appointing an external examiner of a PhD in the biomedical sciences in Sweden: a questionnaire-based survey

A survey of 170 Swedish mentors of PhD-students found that expertise in the research field and avoidance of conflict of interest were big motivators for finding an examiner from abroad for PhD theses. The survey also identified that concern by supervisors for facilitating the career paths of younger scientists in terms of introductions to potential labs for post-doctoral work and obtaining high quality neutral review of one’s research was also important, as was the desire to set up collaborations. An expectation from the management of one’s university of the PR-value of a foreign senior person as examiner also played a part. Although few were willing to admit that PR for one’s own group was a motivating factor. A small fraction of responders expressed concern that, as some of the costs of the PhD-examination were being shifted on to the research groups themselves, this might impact the current situation. Language also played a subordinate role. To get the best out of the visiting examiner, it was important to educate and instruct them in their role in a Swedish PhD-examination protocol. Male supervisors had had more PhD-candidates than female, but they also had used more Sweden-based examiners than their female colleagues. We conclude that using a foreign examiner was motivated by factors that are likely to prevail for the foreseeable future. This Swedish practice may also provide a template for a common standard.     

Some Equivalences between Kernel Methods and Information Theoretic Methods

In this paper, we discuss some equivalences between two recently introduced statistical learning schemes, namely Mercer kernel methods and information theoretic methods. We show that Parzen window-based estimators for some information theoretic cost functions are also cost functions in a corresponding Mercer kernel space. The Mercer kernel is directly related to the Parzen window. Furthermore, we analyze a classification rule based on an information theoretic criterion, and show that this corresponds to a linear classifier in the kernel space. By introducing a weighted Parzen window density estimator, we also formulate the support vector machine in this information theoretic perspective.

---

     

Predictors of Use of Social Network Sites at Work ‐ A Specific Type of Cyberloafing

A total of 11,018 employees participated in a survey investigating whether demographic, personality, and work‐related variables could explain variance in attitudes towards and actual use of social network sites for personal purposes during working hours. Age was negatively related to both dependent variables. Male gender, single status, and education were positively associated with both dependent variables. Managers had negative attitudes to use, but top‐level managers reported more use than other respondents. Access to social network sites at the workplace was positively related to both dependent variables, whereas policies prohibiting showed the opposite relationship. Extraversion and Neuroticism were positively related to both dependent variables. Conscientiousness, positive challenge at work, and quantitative demands were all negatively related to both dependent variables.     

On-Line Chemical Analysis of Individual Alkali-Containing Aerosol Particles by Surface Ionization Combined with Time-of-Flight Mass Spectrometry

An aerosol mass spectrometer for measurements of the alkali metal content in individual submicron aerosol particles is presented. The instrument combines surface ionization of individual particles on a hot platinum surface with orthogonal acceleration time-of-flight mass spectrometry. The instrument simultaneously provides the content of different alkali metal elements in single particles with high sensitivity. The instrument is characterized in laboratory experiments, and determination of the alkali metal content is demonstrated for particle diameters of 50–500 nm. The technique is demonstrated in ambient air measurements at an urban background site, and sea spray particles and particles originating from biomass burning are identified based on their content of sodium and potassium. Possible further improvements and applications of the technique are discussed.     

Multivariate Methods in the Development of a New Tablet Formulation: Excipient Mixtures and Principal Properties

ABSTRACT

A tablet formulation for direct compression has previously been studied using multivariate design. An optimization study of one of the most important tablet properties, disintegration time, revealed that excipients with Principal Properties (PP's) that were predicted as suitable by the model were not represented within the studied material.

The feasibility of using mixtures of excipients in the multivariate approach to tablet formulation to solve this problem has been investigated in the present study. By mixing different excipients of the same excipient class, it should be possible to obtain mixtures with the predicted PP's, which in turn should give a formulation with the desired properties. In order to investigate the utility of this approach, separate mixture designs were applied to both binders and fillers (diluents).

As reported here, the Partial Least Squares Projections to Latent Structures (PLS) model developed in the previously published screening study has been validated in the sense that the interesting region of the PP space identified in it has been shown to contain excipients, pure or mixed, that give the formulation suitable properties. Formulations with suitable properties were found with the mixture experiments. The local models also offer several alternatives for the composition of the formulation that yield the desired disintegration time.