Mechanisms of optical angular momentum transfer to nematic liquid crystalline droplets

A detailed study is presented that evaluates the relative importance of wave plate behavior, scattering processes and absorption phenomena in transferring optical torque from circularly polarized light to optically trapped nematic droplets. A wide range of parameters is considered: droplet diameters between 1 and 15 µm, birefringence values from 0.15 to 0.26 and trapping beam powers from 50 mW to 400 mW. Wave plate behavior is verified through the dependence of torque on droplet diameter and material birefringence. The dependence of the magnitude of the torque on material birefringence confirms the additional importance of the scattering mechanism. Absorption processes are found to be negligible

Adaptive modulation of antibiotic resistance through intragenomic coevolution

Bacteria gain antibiotic resistance genes by horizontal acquisition of mobile genetic elements (MGEs) from other lineages. Newly acquired MGEs are often poorly adapted causing intragenomic conflicts; these are resolved by either compensatory adaptation—of the chromosome or the MGE—or reciprocal coadaptation. The footprints of such intragenomic coevolution are present in bacterial genomes, suggesting an important role promoting genomic integration of horizontally acquired genes, but direct experimental evidence of the process is limited. Here we show adaptive modulation of tetracycline resistance via intrage- nomic coevolution between Escherichia coli and the multidrug resistant plasmid RK2. Tetracycline treatments, including mono- therapy or combination therapies with ampicillin, favoured de novo chromosomal resistance mutations coupled with mutations on RK2 impairing the plasmid-encoded tetracycline efflux pump. These mutations together provided increased tetracycline resistance at reduced cost. Additionally, the chromosomal resistance mutations conferred cross-resistance to chloramphenicol. Reciprocal coadaptation was not observed under ampicillin-only or no antibiotic selection. Intragenomic coevolution can create genomes comprising multiple replicons that together provide high-level, low-cost resistance, but the resulting co-dependence may limit the spread of coadapted MGEs to other lineages

Characterisation of two desiccation-stress related cDNAs TrDr1 and TrDr2 in the resurrection moss Tortula ruralis11The nucleotide sequence reported in this paper appears in EMBL, GenBank and DDBJ Nucleotide Sequence Databases under the accession numbers AI304977 (TrDr1) and AI305064 (TrDr2)

Two EST-derived cDNAs TrDr1 and TrDr2 from Tortula ruralis were identified with significant similarity to psbI encoding the PSII 10kDa protein and the desiccation stress-related cDNA pcC3-06, respectively. RNA blot hybridisation using both total and polysomal RNA fractions was used to analyse TrDr1 and TrDr2 mRNA abundance in response to a desiccation/rehydration cycle. TrDr1 and TrDr2 steady-state transcript levels increased in response to desiccation and preferentially accumulated within the polysomal mRNA fraction. The data suggest that TrDR1 and TrDR2 play a role in vegetative desiccation- tolerance

Ti-TiOx-Pt Metal-Oxide-Metal Diodes Fabricated via a Simple Oxidation Technique

This work presents the successful production, via a simple oxidation process, of Ti-TiOx-Pt Metal-Oxide-Metal diodes with excellent electrical asymmetry. TEM analysis has been used to verify the oxide thickness. A thicker layer produces better diodes, although they are of a less uniform nature. The conduction mechanism in these diodes is still under investigation

A microgripper sensor device capable of detecting ion efflux from whole cells

Electrothermally actuated microgripper sensor devices that are capable of simultaneous manipulation of live mouse oocytes and the sensing of potassium ion efflux are presented. The ion selective electrode technology applied to a microgripper device yielded a first generation ion sensor with competitive characteristics in selectivity, sensitivity, stability and temporal resolution. The microgripper sensor devices could readily detect the 9 ± 3 mM efflux of potassium ions upon mechanical stimulation. This technology is generic and applicable to generating potentiometric and amperometric sensing microgrippers

Origami lesion-targeting device for CT-guided interventions

The objective of this study is to preliminarily evaluate a lesion-targeting device for CT-guided interventions. The device is created by laser cutting the structure from a sheet of medical grade paperboard, 3D printing two radiocontrast agent grids onto the surface and folding the structure into a rectangular prism with a viewing window. An abdominal imaging phantom was used to evaluate the device through CT imaging and the targeting of lesions for needle insertion. The lesion-targeting trials resulted in a mean targeting error of 2.53 mm (SD 0.59 mm, n = 30). The device is rigid enough to adequately support standard biopsy needles, and it attaches to the patient, reducing the risk of tissue laceration by needles held rigidly in place by an external manipulator. Additional advantages include adequate support for the insertion of multiple surgical tools at once for procedures such as composite ablation and the potential to guide off-axial needle insertion. The low-cost and disposability of the device make it well-suited for the minimally invasive image-guided therapy environment

Nonlinear Transient Field Problems with Phase Change using the Boundary Element Method

Peer reviewe

Infection dynamics: from organ to host population

A symposium discussing collaborative research work on infectious diseases dynamics was held at Queens' College, University of Cambridge on 25 October 2006

Is the hyporheic zone a refugium for aquatic macroinvertebrates during severe low flow conditions?

The potential role of the hyporheic zone as a refugium for stream invertebrates during hydrological perturbations was acknowledged more than five decades ago. However, field evidence to support the hyporheic refuge hypothesis during periods of flow recession and severe low flow remains equivocal. Some studies report fauna using the hyporheic zone during periods of flow cessation whilst others have recorded little or no refuge use due to limited habitat availability or harsh abiotic conditions. We assessed aquatic macroinvertebrate community changes associated with severe low flow conditions during a severe supra-seasonal drought on the Little Stour River (UK). Paired benthic and hyporheic samples were collected from four sites (two perennial, two intermittent) on the upper reaches of the river. The number of benthic taxa and the proportion of benthos (particularly the amphipod Gammarus pulex) within the hyporheic zone relative to those in the benthic samples increased significantly during the latter stages of the drought at all sites. These changes coincided with elevated benthic and hyporheic water temperatures rather than a reduction in river discharge alone. The abundance of obligate hypogean macroinvertebrates also increased during the latter stages of the event, suggesting that hypogean taxa may also utilise the shallow hyporheic zone during adverse environmental conditions. Our results, based on paired surface-hyporheic field samples at multiple sites, support the hyporheic refuge hypothesis within a temperate groundwater-dominated stream during severe drought. The results also clearly demonstrate the importance of considering surface-subsurface linkages when assessing responses to disturbance in streams

Distributed Generation and Resilience in Power Grids

We study the effects of the allocation of distributed generation on the resilience of power grids. We find that an unconstrained allocation and growth of the distributed generation can drive a power grid beyond its design parameters. In order to overcome such a problem, we propose a topological algorithm derived from the field of Complex Networks to allocate distributed generation sources in an existing power grid.Comment: proceedings of Critis 2012 http://critis12.hig.no