Phase behavior of hard spheres confined between parallel hard plates: Manipulation of colloidal crystal structures by confinement

We study the phase behavior of hard spheres confined between two parallel hard plates using extensive computer simulations. We determine the full equilibrium phase diagram for arbitrary densities and plate separations from one to five hard-sphere diameters using free energy calculations. We find a first-order fluid-solid transition, which corresponds to either capillary freezing or melting depending on the plate separation. The coexisting solid phase consists of crystalline layers with either triangular or square symmetry. Increasing the plate separation, we find a sequence of crystal structures from n triangular to (n+1) square to (n+1) triangular, where n is the number of crystal layers, in agreement with experiments on colloids. At high densities, the transition between square to triangular phases are intervened by intermediate structures, e.g., prism, buckled, and rhombic phases.Comment: 9 pages, 4 figures. Accepted for publication in J. Phys.: Condens. Matte

Effect of excluded volume interactions on the interfacial properties of colloid-polymer mixtures

We report a numerical study of equilibrium phase-diagrams and interfacial properties of bulk and confined colloid-polymer mixtures using grand canonical Monte Carlo simulations. Colloidal particles are treated as hard spheres, while the polymer chains are described as soft repulsive spheres. The polymer-polymer, colloid-polymer, and wall-polymer interactions are described by density-dependent potentials derived by Bolhuis and Louis [Macromolecules, 35 (2002), p.1860]. We compared our results with those of the Asakura-Oosawa-Vrij model, that treats the polymers as ideal particles. We find that the number of polymers needed to drive the demixing transition is larger for the interacting polymers, and that the gas-liquid interfacial tension is smaller. When the system is confined between two parallel hard plates, we find capillary condensation. Compared with the AOV model, we find that the excluded volume interactions between the polymers suppress capillary condensation. In order to induce capillary condensation, smaller undersaturations and smaller plate separations are needed in comparison with ideal polymers.Comment: 9 pages, 10 figures, accepted for publication in the J. Chem. Phy

What is important to the GP in recognizing acute appendicitis in children:a delphi study

Background: For diagnostic research on appendicitis in registration data, insight is needed in the way GPs generate medical records. We aimed to reach a consensus on the features that GPs consider important in the consultation and medical records when evaluating a child with suspected appendicitis. Methods: We performed a three-round Delphi study among Dutch GPs selected by purposive sampling. An initial feature list was created based on a literature search and features in the relevant Dutch guideline. Finally, using a vignette describing a child who needed later reassessment, we asked participants to complete an online questionnaire about which consultation features should be addressed and recorded. Results: A literature review and Dutch guideline yielded 95 consultation features. All three rounds were completed by 22 GPs, with the final consensus list containing 26 symptoms, 29 physical assessments and signs, 2 additional tests, and 8 further actions (including safety-netting, i.e., informing the patient about when to contact the GP again). Of these, participants reached consensus that 37 should be actively addressed and that 20 need to be recorded if findings are negative. Conclusions: GPs agreed that negative findings do not need to be recorded for most features and that records should include the prognostic and safety-netting advice given. The results have implications in three main domains: for research, that negative findings are likely to be missing; for medicolegal purposes, that documentation cannot be expected to be complete; and for clinical practice, that safety-netting advice should be given and documented.</p

What is important to the GP in recognizing acute appendicitis in children:a delphi study

Background: For diagnostic research on appendicitis in registration data, insight is needed in the way GPs generate medical records. We aimed to reach a consensus on the features that GPs consider important in the consultation and medical records when evaluating a child with suspected appendicitis. Methods: We performed a three-round Delphi study among Dutch GPs selected by purposive sampling. An initial feature list was created based on a literature search and features in the relevant Dutch guideline. Finally, using a vignette describing a child who needed later reassessment, we asked participants to complete an online questionnaire about which consultation features should be addressed and recorded. Results: A literature review and Dutch guideline yielded 95 consultation features. All three rounds were completed by 22 GPs, with the final consensus list containing 26 symptoms, 29 physical assessments and signs, 2 additional tests, and 8 further actions (including safety-netting, i.e., informing the patient about when to contact the GP again). Of these, participants reached consensus that 37 should be actively addressed and that 20 need to be recorded if findings are negative. Conclusions: GPs agreed that negative findings do not need to be recorded for most features and that records should include the prognostic and safety-netting advice given. The results have implications in three main domains: for research, that negative findings are likely to be missing; for medicolegal purposes, that documentation cannot be expected to be complete; and for clinical practice, that safety-netting advice should be given and documented.</p

Influence of open- and closed-book tests on medical students' learning approaches

CONTEXT Two learning approaches are consistently distinguished in the literature: deep and surface learning. The deep learning approach is considered preferable. Open-book tests are expected to stimulate deep learning and to offer a possible way of handling the substantial growth in medical knowledge. In this study we test the hypothesis that open-book tests stimulate deep learning more than closed-book tests. METHODS Medical students in Years 2 (n = 423) and 3 (n = 306) participated in this study. They evaluated their preparation for open- and closed-book tests using the test for Deep Information Processing (DIP). This questionnaire consists of 24 items divided into three subscales: Critical Reading; Broaden One's Context, and Structuring. A paired t-test was used to analyse the data. RESULTS Both cohorts scored significantly higher when preparing for closed-book tests for the overall DIP score and on the Broaden One's Context and Structuring scales. Year 3 students also scored significantly higher on the Critical Reading scale when preparing for closed-book tests. Gender differences were found: women used deeper learning approaches than men. CONCLUSIONS Our hypothesis was not supported. In fact, the opposite was found: closed-book tests stimulated a deep learning approach more than open-book tests. Three possible explanations are: deep learning is particularly necessary for remembering and recalling knowledge; students feel more confident when preparing for closed-book tests, and students are more motivated to study for closed-book tests. The debate on the concept of deep learning in higher education should probably be renewed

Influences of deep learning, need for cognition and preparation time on open- and closed-book test performance

Objectives The ability to master discipline-specific knowledge is one of the competencies medical students must acquire. In this context, 'mastering' means being able to recall and apply knowledge. A way to assess this competency is to use both open- and closed-book tests. Student performance on both tests can be influenced by the way the student processes information. Deep information processing is expected to influence performance positively. The personal preferences of students in relation to how they process information in general (i.e. their level of need for cognition) may also be of importance. In this study, we examined the inter-relatedness of deep learning, need for cognition and preparation time, and scores on open- and closed-book tests. Methods This study was conducted at the University Medical Centre Groningen. Participants were Year 2 students (n = 423). They were asked to complete a questionnaire on deep information processing, a scale for need for cognition on a questionnaire on intellectualism and, additionally, to write down the time they spent on test preparation. We related these measures to the students' scores on two tests, both consisting of open- and closed-book components and used structural equation modelling to analyse the data. Results Both questionnaires were completed by 239 students (57%). The results showed that need for cognition positively influenced both open- and closed-book test scores (beta-coefficients 0.05 and 0.11, respectively). Furthermore, study outcomes measured by open-book tests predicted closed-book test results better than the other way around (beta-coefficients 0.72 and 0.11, respectively). Conclusions Students with a high need for cognition performed better on open- as well as closed-book tests. Deep learning did not influence their performance. Adding open-book tests to the regularly used closed-book tests seems to improve the recall of knowledge that has to be known by heart. Need for cognition may provide a valuable addition to existing theories on learning

Intake of various food groups among girls and boys with different utilisation of school meals

Children and adolescents spend a large part of their time at school, which is why the quality of school meals is of great importance. In this study, the extent to which intakes of various food groups among children and adolescents were in line with the recommendations of the Optimised Mixed Diet (OMD) were examined according to frequency of utilisation of school meals, based on data from the second Eating study as a KiGGS Module (EsKiMo II). Among 6- to 11-year-old boys, more frequent (≥ three times weekly) utilisation of school meals is associated with more frequently meeting or exceeding the OMD recommendation for fruit consumption. The same is true among 12- to 17-year-old girls for eggs and fats/oils used for cooking or spreads, and among 12- to 17-year-old boys for fish. The results from EsKiMo II show that regular uptake of school meals is associated with differences in intakes of various food groups with respect to the OMD recommendations

Formation of dodecagonal quasicrystals in two-dimensional systems of patchy particles

The behaviour of two-dimensional patchy particles with 5 and 7 regularly-arranged patches is investigated by computer simulation. For higher pressures and wider patch widths, hexagonal crystals have the lowest enthalpy, whereas at lower pressures and for narrower patches, lower-density crystals with five nearest neighbours and that are based on the (3^2,4,3,4) tiling of squares and triangles become lower in enthalpy. Interestingly, in regions of parameter space near to that where the hexagonal crystals become stable, quasicrystalline structures with dodecagonal symmetry form on cooling from high temperature. These quasicrystals can be considered as tilings of squares and triangles, and are probably stabilized by the large configurational entropy associated with all the different possible such tilings. The potential for experimentally realizing such structures using DNA multi-arm motifs are discussed.Comment: 12 pages, 12 figure

Treatment Restrictions and the Risk of Death in Patients With Ischemic Stroke or Intracerebral Hemorrhage

BACKGROUND AND PURPOSE: Do-not-resuscitate (DNR) orders in the first 24 hours after intracerebral hemorrhage have been associated with an increased risk of early death. This relationship is less certain for ischemic stroke. We assessed the relation between treatment restrictions and mortality in patients with ischemic stroke and in patients with intracerebral hemorrhage. We focused on the timing of treatment restrictions after admission and the type of treatment restriction (DNR order versus more restrictive care). METHODS: We retrospectively assessed demographic and clinical data, timing and type of treatment restrictions, and vital status at 3 months for 622 consecutive stroke patients primarily admitted to a Dutch university hospital. We used a Cox regression model, with adjustment for age, sex, comorbidities, and stroke type and severity. RESULTS: Treatment restrictions were installed in 226 (36%) patients, more frequently after intracerebral hemorrhage (51%) than after ischemic stroke (32%). In 187 patients (83%), these were installed in the first 24 hours. Treatment restrictions installed within the first 24 hours after hospital admission and those installed later were independently associated with death at 90 days (adjusted hazard ratios, 5.41 [95% CI, 3.17-9.22] and 5.36 [95% CI, 2.20-13.05], respectively). Statistically significant associations were also found in patients with ischemic stroke and in patients with just an early DNR order. In those who died, the median time between a DNR order and death was 520 hours (interquartile range, 53-737). CONCLUSIONS: The strong relation between treatment restrictions (including DNR orders) and death and the long median time between a DNR order and death suggest that this relation may, in part, be causal, possibly due to an overall lack of aggressive care