Label-free microfluidic enrichment of ring-stage Plasmodium falciparum-infected red blood cells using non-inertial hydrodynamic lift

<b>Background</b> Understanding of malaria pathogenesis caused by Plasmodium falciparum has been greatly deepened since the introduction of in vitro culture system, but the lack of a method to enrich ring-stage parasites remains a technical challenge. Here, a novel way to enrich red blood cells containing parasites in the early ring stage is described and demonstrated.<p></p> <b>Methods</b> A simple, straight polydimethylsiloxane microchannel connected to two syringe pumps for sample injection and two height reservoirs for sample collection is used to enrich red blood cells containing parasites in the early ring stage (8-10 h p.i.). The separation is based on the non-inertial hydrodynamic lift effect, a repulsive cell-wall interaction that enables continuous and label-free separation with deformability as intrinsic marker.<p></p> <b>Results</b> The possibility to enrich red blood cells containing P. falciparum parasites at ring stage with a throughput of ~12,000 cells per hour and an average enrichment factor of 4.3 ± 0.5 is demonstrated.<p></p> <b>Conclusion</b> The method allows for the enrichment of red blood cells early after the invasion by P. falciparumparasites continuously and without any need to label the cells. The approach promises new possibilities to increase the sensitivity of downstream analyses like genomic- or diagnostic tests. The device can be produced as a cheap, disposable chip with mass production technologies and works without expensive peripheral equipment. This makes the approach interesting for the development of new devices for field use in resource poor settings and environments, e.g. with the aim to increase the sensitivity of microscope malaria diagnosis.<p></p&gt

Brownian molecular motors driven by rotation-translation coupling

We investigated three models of Brownian motors which convert rotational diffusion into directed translational motion by switching on and off a potential. In the first model a spatially asymmetric potential generates directed translational motion by rectifying rotational diffusion. It behaves much like a conventional flashing ratchet. The second model utilizes both rotational diffusion and drift to generate translational motion without spatial asymmetry in the potential. This second model can be driven by a combination of a Brownian motor mechanism (diffusion driven) or by powerstroke (drift driven) depending on the chosen parameters. In the third model, elements of both the Brownian motor and powerstroke mechanisms are combined by switching between three distinct states. Relevance of the model to biological motor proteins is discussed.Comment: 11 pages, 8 figure

Solving Langevin equation with the bicolour rooted tree method

Stochastic differential equations, especially the one called Langevin equation, play an important role in many fields of modern science. In this paper, we use the bicolour rooted tree method, which is based on the stochastic Taylor expansion, to get the systematic pattern of the high order algorithm for Langevin equation. We propose a popular test problem, which is related to the energy relaxation in the double well, to test the validity of our algorithm and compare our algorithm with other usually used algorithms in simulations. And we also consider the time-dependent Langevin equation with the Ornstein-Uhlenbeck noise as our second example to demonstrate the versatility of our method

How Lego rebuilt and became the top toymaker in the world

Lego is an exemplary case for a classic turnaround that put the company in an even better position in the future. In the past, Lego’s sales increased steadily over the years, however, in the 90s they showed signs of struggle and they reported their first-ever loss in the history of the company. What followed was a turbulent ride for the toymaker. After several attempts that failed, Lego finally managed to change their downward ride drastically and achieve a textbook turnaround. The case will highlight actions that resulted in the turnaround and long-term competitive advantage. Additionally, it will give information about how a change of leadership, especially during a crisis, but also in the long-term, affect the firm’s performance. The case will demonstrate how theoretical concepts come to life and it aims to give students a better understanding by presenting a compelling real-life example and to contribute to the turnaround studies.A Lego é um caso exemplar de um clássico turnaround que colocou a empresa numa posição ainda melhor no futuro. No passado, as vendas da Lego aumentavam de maneira consistente ao longo dos anos, no entanto, nos anos 90 a Lego mostrou os primeiros sinais de dificuldade e reportou a sua primeira perda na história da empresa. O que se seguiu foi uma viagem atribulada para a fabricante de brinquedos. Depois de várias tentativas que falharam, a Lego finalmente conseguiu sair da sua espiral descendente e alcançar drasticamente uma turnaround perfeita. O caso vai destacar as ações que levaram à turnaround e a uma vantagem competitiva a longo prazo. Adicionalmente, o caso apresenta informação sobre como a mudança de liderança, especificamente durante uma crise, mas também a longo prazo, afeta o desempenho da empresa. O caso demonstra como conceitos teóricos ganham vida e visa dar aos alunos uma melhor compreensão de turnarounds através da apresentação de um exemplo interessante de uma situação real e contribuir para o estudo de turnarounds

Software für Meta-Analysen

Diese Arbeit soll einen umfassenden Überblick über die Geschichte der Software für Meta-Analysen geben. Meta-Analysen sind sowohl in den Sozialwissenschaften, als auch in der Medizin und Wirtschaft, mittlerweile ein unabdingbares Mittel zur Auswertung, Datenanalyse und grafischen Darstellung der Daten. Im Weiteren wird das Konzept der Usability erläutert und sechs Programme, die häufig in wissenschaftlichen Arbeiten zum Einsatz kommen, werden hinsichtlich ihrer Usability evaluiert

SpaceTeamSat1 - Giving High-School Students a Hands-On Experience in Space Software Development

Educational Mission Enable high-school students to run software experiments on an educational payload (Raspberry Pi platform) Students will code their programs in Python Code will be sent to CubeSat via RF communication Code will run on educational payload Results will be downlinked and handed over to the students Students will be supported during the entire mission and receive a development kit for codin

Spatiotemporal Dynamics of Dilute Red Blood Cell Suspensions in Low-Inertia Microchannel Flow

Microfluidic technologies are commonly used for the manipulation of red blood cell (RBC) suspensions and analyses of flow-mediated biomechanics. To enhance the performance of microfluidic devices, understanding the dynamics of the suspensions processed within is crucial. We report novel, to our knowledge, aspects of the spatiotemporal dynamics of RBC suspensions flowing through a typical microchannel at low Reynolds number. Through experiments with dilute RBC suspensions, we find an off-center two-peak (OCTP) profile of cells contrary to the centralized distribution commonly reported for low-inertia flows. This is reminiscent of the well-known “tubular pinch effect,” which arises from inertial effects. However, given the conditions of negligible inertia in our experiments, an alternative explanation is needed for this OCTP profile. Our massively parallel simulations of RBC flow in real-size microfluidic dimensions using the immersed-boundary-lattice-Boltzmann method confirm the experimental findings and elucidate the underlying mechanism for the counterintuitive RBC pattern. By analyzing the RBC migration and cell-free layer development within a high-aspect-ratio channel, we show that such a distribution is co-determined by the spatial decay of hydrodynamic lift and the global deficiency of cell dispersion in dilute suspensions. We find a cell-free layer development length greater than 46 and 28 hydraulic diameters in the experiment and simulation, respectively, exceeding typical lengths of microfluidic designs. Our work highlights the key role of transient cell distribution in dilute suspensions, which may negatively affect the reliability of experimental results if not taken into account

Numerical simulations of complex fluid-fluid interface dynamics

Interfaces between two fluids are ubiquitous and of special importance for industrial applications, e.g., stabilisation of emulsions. The dynamics of fluid-fluid interfaces is difficult to study because these interfaces are usually deformable and their shapes are not known a priori. Since experiments do not provide access to all observables of interest, computer simulations pose attractive alternatives to gain insight into the physics of interfaces. In the present article, we restrict ourselves to systems with dimensions comparable to the lateral interface extensions. We provide a critical discussion of three numerical schemes coupled to the lattice Boltzmann method as a solver for the hydrodynamics of the problem: (a) the immersed boundary method for the simulation of vesicles and capsules, the Shan-Chen pseudopotential approach for multi-component fluids in combination with (b) an additional advection-diffusion component for surfactant modelling and (c) a molecular dynamics algorithm for the simulation of nanoparticles acting as emulsifiers.Comment: 24 pages, 12 figure