Design strategies for optimizing holographic optical tweezers setups

We provide a detailed account of the construction of a system of holographic optical tweezers. While much information is available on the design, alignment and calibration of other optical trapping configurations, those based on holography are relatively poorly described. Inclusion of a spatial light modulator in the setup gives rise to particular design trade-offs and constraints, and the system benefits from specific optimization strategies, which we discuss.Comment: 16 pages, 15 figure

Remote effects of acute kidney injury in a porcine model

Background: Acute Kidney Injury (AKI) is a common and serious disease with no specific treatment. An episode of AKI may affect organs distant to the kidney, further increasing the morbidity associated with AKI. The mechanism of organ cross-talk after AKI is unclear. The renal and immune systems of pigs and humans are alike. Using a preclinical animal (porcine) model, we test the hypothesis that early effects of AKI on distant organs is by immune cell infiltration leading to inflammatory cytokine production, extravasation and edema. Study Design: In 29 pigs exposed to either sham-surgery or renal ischemia-reperfusion (control, n=12; AKI, n=17) we assessed remote organ (liver, lung, brain) effects in the short-(from 2 to 48h reperfusion) and longer-term (5 weeks later) using immunofluorescence (for leucocyte infiltration, apoptosis), a cytokine array, tissue elemental analysis (electrolytes), blood hematology and chemistry (e.g. liver enzymes) and PCR (for inflammatory markers). Results: AKI elicited significant, short-term (~24h) increments in enzymes indicative of acute liver damage (e.g. AST:ALT ratio; P=0.02) and influenced tissue biochemistry in some remote organs (e.g. lung tissue [Ca++] increased; P=0.04). These effects largely resolved after 48h and no further histopathology, edema, apoptosis or immune cell infiltration was noted in liver, lung or hippocampus in the short- and longer-term. Conclusions: AKI has subtle biochemical effects on remote organs in the short-term including a transient increment in markers of acute liver damage. These effects resolved by 48h and no further remote organ histopathology, apoptosis, edema or immune cell infiltration was noted

Signal transduction pathways involved in proteolysis-inducing factor induced proteasome expression in murine myotubes

The proteolysis-inducing factor (PIF) is produced by cachexia-inducing tumours and initiates protein catabolism in skeletal muscle. The potential signalling pathways linking the release of arachidonic acid (AA) from membrane phospholipids with increased expression of the ubiquitin-proteasome proteolytic pathway by PIF has been studied using C2C12 murine myotubes as a surrogate model of skeletal muscle. The induction of proteasome activity and protein degradation by PIF was blocked by quinacrine, a nonspecific phospholipase A2 (PLA2) inhibitor and trifluroacetyl AA, an inhibitor of cytosolic PLA2. PIF was shown to increase the expression of calcium-independent cytosolic PLA2, determined by Western blotting, at the same concentrations as those inducing maximal expression of 20S proteasome α-subunits and protein degradation. In addition, both U-73122, which inhibits agonist-induced phospholipase C (PLC) activation and D609, a specific inhibitor of phosphatidylcholine-specific PLC also inhibited PIF-induced proteasome activity. This suggests that both PLA 2 and PLC are involved in the release of AA in response to PIF, and that this is important in the induction of proteasome expression. The two tyrosine kinase inhibitors genistein and tryphostin A23 also attenuated PIF-induced proteasome expression, implicating tyrosine kinase in this process. PIF induced phosphorylation of p44/42 mitogen-activated protein kinase (MAPK) at the same concentrations as that inducing proteasome expression, and the effect was blocked by PD98059, an inhibitor of MAPK kinase, as was also the induction of proteasome expression, suggesting a role for MAPK activation in PIF-induced proteasome expression. © 2003 Cancer Research UK

Redefining innovation processes: The digital designers at work

As design in digital innovation has become a thing, we highlight the inconclusive concepts that describe design activity in innovation processes. Proposing an alternative theoretical lens - a sociomaterial practice lens - we claim that this view can reveal the contribution of digital designers to the work of innovation. This paper draws on a research study with digital designers in the UK. At the same time as we begin to reconceptualise the ways digital design activity can be described, we also illustrate a theoretical framework based on 1) action and knowing as ordered by collectively produced objects, 2) sociomateriality and the configuration of human bodies and materials in action, 3) the co-emergence of objects and sociomaterial configurations where each is the condition of the other. This alternative way of looking at design activity may pose some challenges to the theoretical traditions in the field. We however believe that it contains immense potential too

Unfolding and refolding properties of S pili on extraintestinal pathogenic Escherichia coli

International audienceS pili are members of the chaperone-usher-pathway-assembled pili family that are predominantly associated with neonatal meningitis (S(II)) and believed to play a role in ascending urinary tract infections (S(I)). We used force-measuring optical tweezers to characterize the intrinsic biomechanical properties and kinetics of S(II) and S(I) pili. Under steady-state conditions, a sequential unfolding of the layers in the helix-like rod occurred at somewhat different forces, 26 pN for S(II) pili and 21 pN for S(I) pili, and there was an apparent difference in the kinetics, 1.3 and 8.8 Hz. Tests with bacteria defective in a newly recognized sfa gene (sfaX (II)) indicated that absence of the sfaX (II) gene weakens the interactions of the fimbrium slightly and decreases the kinetics. Data of S(I) are compared with those of previously assessed pili primary associated with urinary tract infections, the P and type 1 pili. S pili have weaker layer-to-layer bonds than both P and type 1 pili, 21, 28 and 30 pN, respectively. In addition, the S pili kinetics are ~10 times faster than the kinetics of P pili and ~550 times faster than the kinetics of type 1 pili. Our results also show that the biomechanical properties of pili expressed ectopically from a plasmid in a laboratory strain (HB101) and pili expressed from the chromosome of a clinical isolate (IHE3034) are identical. Moreover, we demonstrate that it is possible to distinguish, by analyzing force-extension data, the different types of pili expressed by an individual cell of a clinical bacterial isolate

Finding-NEVO: toward radical design in HCI

Abstract. We address the methodology of design-oriented research in HCI, whereby researchers design and implement technology to test concepts. The task is to produce a testable prototype (that we call NEVO, Non-Embarrassing Version One) that faithfully embodies the concept. We probed leading HCI researchers and CHI authors about the challenge of Finding NEVO. We found uncertainty on how to design prototypes that allow for both design and scientific contributions. We propose the Finding-NEVO model that articulates a process yielding prototypes that are faithful to the rationale and idea being studied. We conclude by discussing our theoretical and methodological contributions