Impact of elasticity on the piezoresponse of adjacent ferroelectric domains investigated by scanning force microscopy

As a consequence of elasticity, mechanical deformations of crystals occur on a length scale comparable to their thickness. This is exemplified by applying a homogeneous electric field to a multi-domain ferroelectric crystal: as one domain is expanding the adjacent ones are contracting, leading to clamping at the domain boundaries. The piezomechanically driven surface corrugation of micron-sized domain patterns in thick crystals using large-area top electrodes is thus drastically suppressed, barely accessible by means of piezoresponse force microscopy

The influence of turbulence on the aerodynamic optimisation of bluff body road vehicles

In order to promote further understanding of the effects of the atmospheric environment encountered by road vehicles in the real world, a wind tunnel based investigation was conducted into the effect of small scale turbulence on the road vehicle optimisation process. An initial investigation was carried out using a I-box model with variable leading edge radii from 10mm to 100mm. Measurements of time averaged forces were made over a range of Reynolds numbers from 200,000 to 1,300,000 (based on the square root of frontal area) and free stream turbulence levels from 0.2% to 5.1%. The transcritical Reynolds number based on edge radius was established as a basis for comparison between turbulence levels. Centreline pressures and PlV vector fields are presented to provide information on separation and reattachment. The investigation was extended to a more representative 2-box model using the same radii as before and a reference model at full scale, where the edge radii varied from 25mm to 150mm and turbulence intensity from 1.8% to 4.3%. It was shown that there is a strong reduction of separation under increased turbulence, and a small increase in skin friction. A further experiment was carried out to investigate the influence of freestream turbulence on the characteristic effect of changing backIight angle on lift and drag. It is shown that there was a reduction in drag due to the action of turbulence on the separation over the backIight, which may be driven by an effect on vortex strength. Tests were also carried out on two full scale vehicles to investigate the effect of increasing turbulence intensity on front and rear spoilers, cooling drag, and A-pillar vortex flows. The observed changes were small but would often be cumulative in their effect, so that optimising a vehicle in a significantly different turbulence level could produce a difference in the total forces acting on the vehicle. These experiments have shown that the primary effect of the additional freestream turbulence introduced by grids is on the boundary layer, as was expected from the literature. The results showed that increasing the turbulence intensity made separated regions smaller, and suggested that vortices become weaker and less well defined. The work provides a basis for continuing to investigate the effect of freestream turbulence on the process of optimising the aerodynamics of road vehicles.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Oral, nasal and pharyngeal exposure to lipopolysaccharide causes a fetal inflammatory response in sheep.

BackgroundA fetal inflammatory response (FIR) in sheep can be induced by intraamniotic or selective exposure of the fetal lung or gut to lipopolysaccharide (LPS). The oral, nasal, and pharyngeal cavities (ONP) contain lymphoid tissue and epithelium that are in contact with the amniotic fluid. The ability of the ONP epithelium and lymphoid tissue to initiate a FIR is unknown.ObjectiveTo determine if FIR occurs after selective ONP exposure to LPS in fetal sheep.MethodsUsing fetal recovery surgery, we isolated ONP from the fetal lung, GI tract, and amniotic fluid by tracheal and esophageal ligation and with an occlusive glove fitted over the snout. LPS (5 mg) or saline was infused with 24 h Alzet pumps secured in the oral cavity (n = 7-8/group). Animals were delivered 1 or 6 days after initiation of the LPS or saline infusions.ResultsThe ONP exposure to LPS had time-dependent systemic inflammatory effects with changes in WBC in cord blood, an increase in posterior mediastinal lymph node weight at 6 days, and pro-inflammatory mRNA responses in the fetal plasma, lung, and liver. Compared to controls, the expression of surfactant protein A mRNA increased 1 and 6 days after ONP exposure to LPS.ConclusionONP exposure to LPS alone can induce a mild FIR with time-dependent inflammatory responses in remote fetal tissues not directly exposed to LPS

Ipl1/Aurora B kinase coordinates synaptonemal complex disassembly with cell cycle progression and crossover formation in budding yeast meiosis

Several protein kinases collaborate to orchestrate and integrate cellular and chromosomal events at the G2/M transition in both mitotic and meiotic cells. During the G2/M transition in meiosis, this includes the completion of crossover recombination, spindle formation, and synaptonemal complex (SC) breakdown. We identified Ipl1/Aurora B kinase as the main regulator of SC disassembly. Mutants lacking Ipl1 or its kinase activity assemble SCs with normal timing, but fail to dissociate the central element component Zip1, as well as its binding partner, Smt3/SUMO, from chromosomes in a timely fashion. Moreover, lack of Ipl1 activity causes delayed SC disassembly in a cdc5 as well as a CDC5-inducible ndt80 mutant. Crossover levels in the ipl1 mutant are similar to those observed in wild type, indicating that full SC disassembly is not a prerequisite for joint molecule resolution and subsequent crossover formation. Moreover, expression of meiosis I and meiosis II-specific B-type cyclins occur normally in ipl1 mutants, despite delayed formation of anaphase I spindles. These observations suggest that Ipl1 coordinates changes to meiotic chromosome structure with resolution of crossovers and cell cycle progression at the end of meiotic prophase

Contrast Mechanisms for the Detection of Ferroelectric Domains with Scanning Force Microscopy

We present a full analysis of the contrast mechanisms for the detection of ferroelectric domains on all faces of bulk single crystals using scanning force microscopy exemplified on hexagonally poled lithium niobate. The domain contrast can be attributed to three different mechanisms: i) the thickness change of the sample due to an out-of-plane piezoelectric response (standard piezoresponse force microscopy), ii) the lateral displacement of the sample surface due to an in-plane piezoresponse, and iii) the electrostatic tip-sample interaction at the domain boundaries caused by surface charges on the crystallographic y- and z-faces. A careful analysis of the movement of the cantilever with respect to its orientation relative to the crystallographic axes of the sample allows a clear attribution of the observed domain contrast to the driving forces respectively.Comment: 8 pages, 8 figure

The effect of energetic electron precipitation on middle mesospheric night-time ozone during and after a moderate geomagnetic storm

Using a ground-based microwave radiometer at Troll Station, Antarctica (72°S, 2.5°E, L = 4.76), we have observed a decrease of 20–70% in the mesospheric ozone, coincident with increased nitric oxide, between 60 km and 75 km altitude associated with energetic electron precipitation (E > 30 keV) during a moderate geomagnetic storm (minimum Dst of −79 nT) in late July 2009. NOAA satellite data were used to identify the precipitating particles and to characterize their energy, spatial distribution and temporal variation over Antarctica during this isolated storm. Both the ozone decrease and nitric oxide increase initiate with the onset of the storm, and persist for several days after the precipitation ends, descending in the downward flow of the polar vortex. These combined data present a unique case study of the temporal and spatial morphology of chemical changes induced by electron precipitation during moderate geomagnetic storms, indicating that these commonplace events can cause significant effects on the middle mesospheric ozone distribution

Solution structure of a bacterial microcompartment targeting peptide and its application in the construction of an ethanol bioreactor

Targeting of proteins to bacterial microcompartments (BMCs) is mediated by an 18-amino-acid peptide sequence. Herein, we report the solution structure of the N-terminal targeting peptide (P18) of PduP, the aldehyde dehydrogenase associated with the 1,2-propanediol utilization metabolosome from Citrobacter freundii. The solution structure reveals the peptide to have a well-defined helical conformation along its whole length. Saturation transfer difference and transferred NOE NMR has highlighted the observed interaction surface on the peptide with its main interacting shell protein, PduK. By tagging both a pyruvate decarboxylase and an alcohol dehydrogenase with targeting peptides, it has been possible to direct these enzymes to empty BMCs in vivo and to generate an ethanol bioreactor. Not only are the purified, redesigned BMCs able to transform pyruvate into ethanol efficiently, but the strains containing the modified BMCs produce elevated levels of alcohol