The conformation and diffusion of a single DNA molecule confined between two parallel plates are examined using both single molecule experiments and Brownian dynamics simulations accounting for hydrodynamic interactions. The degree of chain stretching and the diffusivity are characterized as a function of the chain confinement and the channel geometry. Good agreement is found between the simulations, experiments, and scaling theory predictions.

Inkjet dispensing is a promising method for patterning cells and biomaterials for tissue engineering applications. In a novel approach, this work uses a biocompatible surfactant to improve the reliability of droplet formation in piezoelectric drop-on-demand inkjet printing of Hep G2 hepatocytes onto hydrogels. During a long printing process, cell aggregation and sedimentation within the inkjet reservoir can lead to inconsistent printing results. In order to improve repeatability, the effects of gentle agitation on cell sedimentation and aggregation within the inkjet reservoir were also investigated. Cell viability and proliferation when printed onto prepared collagen substrates were assessed using live/dead staining and the Alamar Blue metabolic assay. The addition of 0.05% Pluronic as a surfactant did not reduce cell viability, which remained above 95% 2 days after printing. The surfactant improved the reliability of droplet formation. Although gentle stirring of the inkjet reservoir was sufficient to maintain a cell suspension and reduce sedimentation, aggregation within the suspension continued to affect printing performance over a 180 min printing period.

Abstract. Although manual and programmable home thermostats can save energy when used properly, studies have shown that over 40% of U.S. homes may not use energy-saving temperature setbacks when homes are unoccupied. We propose a system for augmenting these thermostats using just-in-time heating and cooling based on travel-to-home distance obtained from location-aware mobile phones. Analyzing GPS travel data from 8 participants (8-12 weeks each) and heating and cooling characteristics from 5 homes, we report results of running computer simulations estimating potential energy savings from such a device. Using a GPSenabled thermostat might lead to savings of as much as 7% for some households that do not regularly use the temperature setback afforded by manual and programmable thermostats. Significantly, these savings could be obtained without requiring any change in occupant behavior or comfort level, and the technology could be implemented affordably by exploiting the ubiquity of mobile phones. Additional savings may be possible with modest context-sensitive prompting. We report on design considerations identified during a pilot test of a fully-functional implementation of the system.

We demonstrate a microfluidic system for long-term tumor cell culture and drug testing. Three-dimensional cell culture is critical in characterizing anticancer treatments since it may provide a better model than monolayer culture of tumor cells. Breast tumor cells were encapsulated within alginate which was gelled in situ within the microchannels. Tumor spheroid formation was observed several days after cell seeding, and various concentrations of doxorubicin were applied to the encapsulated cell aggregates. Drug effects on cell viability and proliferation were measured. In future, hydrogel-based microfluidic devices can comprise part of systems which replace labor intensive screening platforms currently implemented in the laboratory, and they address a need for improving preclinical testing of cancer cell sensitivity to anti-cancer drugs.

Context. In order to better understand the underlying processes and prerequisites for solar activity, it is essential to study the time evolution of the coronal magnetic field of solar active regions (ARs) associated with flare activity. Aims. We investigate the coronal magnetic energy and helicity budgets of ten solar ARs around the times of large flares. In particular, we are interested in a possible relation of the derived quantities to the particular type of the flares that the AR produces, namely, whether they are associated with a CME or whether they are confined (i.e., not accompanied by a CME). Methods. Using an optimization approach, we employed time series of 3D nonlinear force-free magnetic field models of ten ARs, covering a time span of several hours around the time of occurrence of large solar flares (GOES class M1.0 and larger). We subsequently computed the 3D magnetic vector potentials associated to the model 3D coronal magnetic field using a finite-volume method. This allows us to correspondingly compute the coronal magnetic energy and helicity budgets, as well as related (intensive) quantities such as the relative contribution of free magnetic energy, EF/E (energy ratio), the fraction of non-potential (current-carrying) helicity, |HJ|/|HV| (helicity ratio), and the normalized current-carrying helicity, |HJ|/ϕ′2. Results. The total energy and helicity budgets of flare-productive ARs (extensive parameters) cover a broad range of magnitudes, with no obvious relation to the eruptive potential of the individual ARs, that is, whether or not a CME is produced in association with the flare. The intensive eruptivity proxies, EF/E and |HJ|/|HV|, and |HJ|/ϕ′2, however, seem to be distinctly different for ARs that produce CME-associated large flares compared to those which produce confined flares. For the majority of ARs in our sample, we are able to identify characteristic pre-flare magnitudes of the intensive quantities that are clearly associated with subsequent CME-productivity. Conclusions. If the corona of an AR exhibits characteristic values of ⟨|HJ|/|HV|⟩ > 0.1, ⟨EF/E⟩ > 0.2, and ⟨|HJ|/ϕ′2⟩ > 0.005, then the AR is likely to produce large CME-associated flares. Conversely, confined large flares tend to originate from ARs that exhibit coronal values of ⟨|HJ|/|HV|⟩ ≲ 0.1, ⟨EF/E⟩ ≲ 0.1, and ⟨|HJ|/ϕ′2⟩ ≲ 0.002.