Rapid Spatial Mapping of Focused Ultrasound Fields Using a Planar Fabry-Pérot Sensor

Measurement of high acoustic pressures is necessary in order to fully characterise clinical high-intensity focused ultrasound (HIFU) fields, and for accurate validation of computational models of ultrasound propagation. However, many existing measurement devices are unable to withstand the extreme pressures generated in these fields, and those that can often exhibit low sensitivity. Here, a planar Fabry-Pérot interferometer with hard dielectric mirrors and spacer was designed, fabricated, and characterised and its suitability for measurement of nonlinear focused ultrasound fields was investigated. The noise equivalent pressure of the scanning system scaled with the adjustable pressure detection range between 49 kPa for pressures up to 8 MPa and 152 kPa for measurements up to 25 MPa, over a 125 MHz measurement bandwidth. Measurements of the frequency response of the sensor showed that it varied by less than 3 dB in the range 1 - 62 MHz. The effective element size of the sensor was 65 μm and waveforms were acquired at a rate of 200 Hz. The device was used to measure the acoustic pressure in the field of a 1.1 MHz single element spherically focused bowl transducer. Measurements of the acoustic field at low pressures compared well with measurements made using a PVDF needle hydrophone. At high pressures, the measured peak focal pressures agreed well with the focal pressure modelled using the Khokhlov-Zabolotskaya-Kuznetsov equation. Maximum peak positive pressures of 25 MPa, and peak negative pressures of 12 MPa were measured, and planar field scans were acquired in scan times on the order of 1 minute. The properties of the sensor and scanning system are well suited to measurement of nonlinear focused ultrasound fields, in both the focal region and the low pressure peripheral regions. The fast acquisition speed of the system and its low noise equivalent pressure are advantageous, and with further development of the sensor, it has potential in application to HIFU metrology

ABCD transfer matrix model of Gaussian beam propagation in plano-concave optical microresonators

Plano-concave optical microresonators (PCMRs) are optical microcavities formed of one planar and one concave mirror separated by a spacer. PCMRs illuminated by Gaussian laser beams are used as sensors and filters in fields including quantum electrodynamics, temperature sensing, and photoacoustic imaging. To predict characteristics such as the sensitivity of PCMRs, a model of Gaussian beam propagation through PCMRs based on the ABCD matrix method was developed. To validate the model, interferometer transfer functions (ITFs) calculated for a range of PCMRs and beams were compared to experimental measurements. A good agreement was observed, suggesting the model is valid. It could therefore constitute a useful tool for designing and evaluating PCMR systems in various fields. The computer code implementing the model has been made available online

The transcriptome of the novel dinoflagellate Oxyrrhis marina (Alveolata: Dinophyceae): response to salinity examined by 454 sequencing

This is the final version of the article. Available from [BioMed Central via the DOI in this record.BACKGROUND: The heterotrophic dinoflagellate Oxyrrhis marina is increasingly studied in experimental, ecological and evolutionary contexts. Its basal phylogenetic position within the dinoflagellates make O. marina useful for understanding the origin of numerous unusual features of the dinoflagellate lineage; its broad distribution has lent O. marina to the study of protist biogeography; and nutritive flexibility and eurytopy have made it a common lab rat for the investigation of physiological responses of marine heterotrophic flagellates. Nevertheless, genome-scale resources for O. marina are scarce. Here we present a 454-based transcriptome survey for this organism. In addition, we assess sequence read abundance, as a proxy for gene expression, in response to salinity, an environmental factor potentially important in determining O. marina spatial distributions. RESULTS: Sequencing generated ~57 Mbp of data which assembled into 7, 398 contigs. Approximately 24% of contigs were nominally identified by BLAST. A further clustering of contigs (at ≥ 90% identity) revealed 164 transcript variant clusters, the largest of which (Phosphoribosylaminoimidazole-succinocarboxamide synthase) was composed of 28 variants displaying predominately synonymous variation. In a genomic context, a sample of 5 different genes were demonstrated to occur as tandem repeats, separated by short (~200-340 bp) inter-genic regions. For HSP90 several intergenic variants were detected suggesting a potentially complex genomic arrangement. In response to salinity, analysis of 454 read abundance highlighted 9 and 20 genes over or under expressed at 50 PSU, respectively. However, 454 read abundance and subsequent qPCR validation did not correlate well - suggesting that measures of gene expression via ad hoc analysis of sequence read abundance require careful interpretation. CONCLUSION: Here we indicate that tandem gene arrangements and the occurrence of multiple transcribed gene variants are common and indicate potentially complex genomic arrangements in O. marina. Comparison of the reported data set with existing O. marina and other dinoflagellates ESTs indicates little sequence overlap likely as a result of the relatively limited extent of genome scale sequence data currently available for the dinoflagellates. This is one of the first 454-based transcriptome surveys of an ancestral dinoflagellate taxon and will undoubtedly prove useful for future comparative studies aimed at reconstructing the origin of novel features of the dinoflagellates.This work was supported by a NERC grant (NE/F005237/1) awarded to PCW, DJSM, and CDL. We would like to thank Dr Margret Hughes of the Liverpool CGR for conducting 454 sequencing, and Dr Kevin Ashelford for invaluable scripting and bioinformatics support

Stellar Disk Truncations: Where do we stand ?

In the light of several recent developments we revisit the phenomenon of galactic stellar disk truncations. Even 25 years since the first paper on outer breaks in the radial light profiles of spiral galaxies, their origin is still unclear. The two most promising explanations are that these 'outer edges' either trace the maximum angular momentum during the galaxy formation epoch, or are associated with global star formation thresholds. Depending on their true physical nature, these outer edges may represent an improved size characteristic (e.g., as compared to D_25) and might contain fossil evidence imprinted by the galaxy formation and evolutionary history. We will address several observational aspects of disk truncations: their existence, not only in normal HSB galaxies, but also in LSB and even dwarf galaxies; their detailed shape, not sharp cut-offs as thought before, but in fact demarcating the start of a region with a steeper exponential distribution of starlight; their possible association with bars; as well as problems related to the line-of-sight integration for edge-on galaxies (the main targets for truncation searches so far). Taken together, these observations currently favour the star-formation threshold model, but more work is necessary to implement the truncations as adequate parameters characterising galactic disks.Comment: LaTeX, 10 pages, 6 figures, presented at the "Penetrating Bars through Masks of Cosmic Dust" conference in South Africa, proceedings published by Kluwer, and edited by Block, D.L., Freeman, K.C., Puerari, I., & Groess, R; v3 to match published versio

Immunogenicity of antigens from the TbD1 region present in M. africanum and missing from "modern" M. tuberculosis: a cross- sectional study

<p>Abstract</p> <p>Background</p> <p>Currently available tools cannot be used to distinguish between sub-species of the <it>M. tuberculosis </it>complex causing latent tuberculosis (TB) infection. <it>M. africanum </it>causes up to half of TB in West- Africa and its relatively lower progression to disease suggests the presence of a large reservoir of latent infection relative to <it>M. tuberculosis</it>.</p> <p>Methods</p> <p>We assessed the immunogenicity of the TbD1 region, present in <it>M. africanum </it>and absent from "modern" <it>M. tuberculosis</it>, in an ELISPOT assay using cells from confirmed <it>M. africanum </it>or <it>M. tuberculosis </it>infected TB patients without HIV infection in the Gambia.</p> <p>Results</p> <p>Antigens from the TbD1 region induced IFNγ responses in only 35% patients and did not discriminate between patients infected with <it>M. africanum </it>vs. <it>M. tuberculosis</it>, while PPD induced universally high responses.</p> <p>Conclusions</p> <p>Further studies will need to assess other antigens unique to <it>M. africanum </it>that may induce discriminatory immune responses.</p

Effects of removal of dietary polyunsaturated fatty acids on plasma extravasation and mechanical allodynia in a trigeminal neuropathic pain model

<p>Abstract</p> <p>Background</p> <p>Neuropathic pain (NP) is partially mediated by neuroinflammatory mechanisms, and also modulates local neurogenic inflammation. Dietary lipids, in particular the total amount and relative proportions of polyunsaturated fatty acids (PUFAs) of the ω-3 and ω-6 families, have been reported to modify the threshold for thermal and mechanical allodynia in the partial sciatic nerve ligation model of NP in rats. The effects of dietary lipids on other popular NP models, such as the chronic constriction injury (CCI), have not yet been examined. It is also unknown whether dietary PUFAs exert any effect on the capsaicin (CAP)-induced neurogenic inflammation under control or NP conditions. In this study we investigated these interrelated phenomena in the trigeminal territory, which has been much less explored, and for which not all data derived from limb nerves can be directly applied.</p> <p>Results</p> <p>We studied the effects of a CCI of the infraorbital nerve (IoN) on the development of mechanical allodynia and CAP-induced plasma extravasation in rats fed either a regular diet (RD), or a modified diet (MD) with much lower total content and ω-3:ω-6 ratio of PUFAs. In rats kept on MD, mechanical allodynia following CCI-IoN was more pronounced and developed earlier. Extravasation was substantially increased in naive rats fed MD, and displayed differential diet-depending changes one and four weeks after CCI-IoN. When compared with basal levels (in naive and/or sham cases), the net effect of CCI-IoN on ipsilateral extravasation was a reduction in the MD group, but an increase in the RD group, effectively neutralizing the original intergroup differences.</p> <p>Conclusion</p> <p>In summary, PUFA intake reduces CAP-induced neurogenic plasma extravasation in the trigeminal territory, and their removal significantly alters the mechanical allodynia and the plasma extravasation that result from a unilateral CCI-IoN. It is likely that this "protective" effect of dietary lipids is temporary. Also, the presence of contralateral effects of CCI-IoN precludes using the contralateral side as control.</p

Laser-Stimulated Fluorescence in Paleontology

Fluorescence using ultraviolet (UV) light has seen increased use as a tool in paleontology over the last decade. Laser-stimulated fluorescence (LSF) is a next generation technique that is emerging as a way to fluoresce paleontological specimens that remain dark under typical UV. A laser’s ability to concentrate very high flux rates both at the macroscopic and microscopic levels results in specimens fluorescing in ways a standard UV bulb cannot induce. Presented here are five paleontological case histories that illustrate the technique across a broad range of specimens and scales. Novel uses such as back-lighting opaque specimens to reveal detail and detection of specimens completely obscured by matrix are highlighted in these examples. The recent cost reductions in medium-power short wavelength lasers and use of standard photographic filters has now made this technique widely accessible to researchers. This technology has the potential to automate multiple aspects of paleontology, including preparation and sorting of microfossils. This represents a highly cost-effective way to address paleontology's preparatory bottleneck.published_or_final_versio

Wnt Signaling Through Nitric Oxide Synthase Promotes the Formation of Multi-Innervated Spines

Structural plasticity of synapses correlates with changes in synaptic strength. Dynamic modifications in dendritic spine number and size are crucial for long-term potentiation (LTP), the cellular correlate of learning and memory. Recent studies have suggested the generation of multi-innervated spines (MIS), in the form of several excitatory presynaptic inputs onto one spine, are crucial for hippocampal memory storage. However, little is known about the molecular mechanisms underlying MIS formation and their contribution to LTP. Using 3D enhanced resolution confocal images, we examined the contribution of Wnt synaptic modulators in MIS formation in the context of LTP. We show that blockage of endogenous Wnts with specific Wnt antagonists supresses the formation of MIS upon chemical LTP induction in cultured hippocampal neurons. Gain- and loss-of-function studies demonstrate that Wnt7a signaling promotes MIS formation through the postsynaptic Wnt scaffold protein Disheveled 1 (Dvl1) by stimulating neuronal nitric oxide (NO) synthase (nNOS). Subsequently, NO activates soluble guanylyl cyclase (sGC) to increase MIS formation. Consistently, we observed an enhanced frequency and amplitude of excitatory postsynaptic currents. Collectively, our findings identify a unique role for Wnt secreted proteins through nNOS/NO/sGC signaling to modulate MIS formation during LTP