Tracking environmental trends in the Great Bay Estuarine System through comparisons of historical and present-day green and red algal community structure and nutrient content

Monitoring macroalgae populations is an effective means of detecting long term water quality changes in estuarine systems. To investigate the environmental status of New Hampshire’s Great Bay National Estuarine Research Reserve, this study assessed the abundance/distribution of macrophytes, particularly Gracilaria and Ulva species, relative to eutrophication patterns; compared historical (1970s-1990s) and current algal biomass/cover at several sites; and compared Ulva and Gracilaria tissue N/P content to ambient and historical levels. Ulva and Gracilaria biomass/cover have increased significantly at several sites. Cover by Ulva species, at seasonal maxima, was over 90 times the value recorded in the 1970s at Lubberland Creek, and exceeded 50% at all sites in the upper estuary. Gracilaria cover was greater than 25% at Depot Road in the upper estuary, whereas the historical measure was 1%. Sequencing of ITS2, rbcL and CO1 revealed the presence of previously undetected Ulva and Gracilaria species, including Gracilaria vermiculophylla (Ohmi) Papenfuss, an invasive species of Asian origin. Gracilaria vermiculophylla has exceeded G. tikvahiae as the dominant Gracilaria species in Great Bay. Historical voucher specimen screening suggests G. vermiculophylla was introduced as recently as 2003. Nitrogen and phosphorus levels are elevated in the estuary. We should expect continued seasonal nuisance algal blooms

Programmable active pixel sensor to investigate neural interactions within the retina

Detection of the visual scene by the eye and the resultant neural interactions of the retina-brain system give us our perception of sight. We have developed an Active Pixel Sensor (APS) to be used as a tool for both furthering understanding of these interactions via experimentation with the retina and to make developments towards a realisable retinal prosthesis. The sensor consists of 469 pixels in a hexagonal array. The pixels are interconnected by a programmable neural network to mimic lateral interactions between retinal cells. Outputs from the sensor are in the form of biphasic current pulse trains suitable to stimulate retinal cells via a biocompatible array. The APS will be described with initial characterisation and test results

Large-scale multielectrode recording and stimulation of neural activity

Large circuits of neurons are employed by the brain to encode and process information. How this encoding and processing is carried out is one of the central questions in neuroscience. Since individual neurons communicate with each other through electrical signals (action potentials), the recording of neural activity with arrays of extracellular electrodes is uniquely suited for the investigation of this question. Such recordings provide the combination of the best spatial (individual neurons) and temporal (individual action-potentials) resolutions compared to other large-scale imaging methods. Electrical stimulation of neural activity in turn has two very important applications: it enhances our understanding of neural circuits by allowing active interactions with them, and it is a basis for a large variety of neural prosthetic devices. Until recently, the state-of-the-art in neural activity recording systems consisted of several dozen electrodes with inter-electrode spacing ranging from tens to hundreds of microns. Using silicon microstrip detector expertise acquired in the field of high-energy physics, we created a unique neural activity readout and stimulation framework that consists of high-density electrode arrays, multi-channel custom-designed integrated circuits, a data acquisition system, and data-processing software. Using this framework we developed a number of neural readout and stimulation systems: (1) a 512-electrode system for recording the simultaneous activity of as many as hundreds of neurons, (2) a 61-electrode system for electrical stimulation and readout of neural activity in retinas and brain-tissue slices, and (3) a system with telemetry capabilities for recording neural activity in the intact brain of awake, naturally behaving animals. We will report on these systems, their various applications to the field of neurobiology, and novel scientific results obtained with some of them. We will also outline future directions

Depth-specific optogenetic control in vivo with a scalable, high density µLED neural probe

Controlling neural circuits is a powerful approach to uncover a causal link between neural activity and behaviour. Optogenetics has been widely adopted by the neuroscience community as it offers cell-type-specific perturbation with millisecond precision. However, these studies require light delivery in complex patterns with cellular-scale resolution, while covering a large volume of tissue at depth in vivo. Here we describe a novel high-density silicon-based microscale light-emitting diode (µLED) array, consisting of up to ninety-six 25 µm-diameter µLEDs emitting at a wavelength of 450 nm with a peak irradiance of 400 mW/mm2. A width of 100 µm, tapering to a 1 µm point, and a 40 µm thickness help minimise tissue damage during insertion. Thermal properties permit a set of optogenetic operating regimes, with ~0.5°C average temperature increase. We demonstrate depth-dependent activation of mouse neocortical neurons in vivo, offering an inexpensive novel tool for the precise manipulation of neural activity

Predictive validity of the UK clinical aptitude test in the final years of medical school:a prospective cohort study

Peer reviewedPublisher PD

Position Reconstruction in Drift Chambers operated with Xe, CO2 (15%)

We present measurements of position and angular resolution of drift chambers operated with a Xe,CO$_2$(15%) mixture. The results are compared to Monte Carlo simulations and important systematic effects, in particular the dispersive nature of the absorption of transition radiation and non-linearities, are discussed. The measurements were carried out with prototype drift chambers of the ALICE Transition Radiation Detector, but our findings can be generalized to other drift chambers with similar geometry, where the electron drift is perpendicular to the wire planes.Comment: 30 pages, 18 figure

Thermal and optical characterization of micro-LED probes for in vivo optogenetic neural stimulation

Within optogenetics there is a need for compact light sources that are capable of delivering light with excellent spatial, temporal, and spectral resolution to deep brain structures. Here, we demonstrate a custom GaN-based LED probe for such applications and the electrical, optical, and thermal properties are analyzed. The output power density and emission spectrum were found to be suitable for stimulating channelrhodopsin-2, one of the most common light-sensitive proteins currently used in optogenetics. The LED device produced high light intensities, far in excess of those required to stimulate the light-sensitive proteins within the neurons. Thermal performance was also investigated, illustrating that a broad range of operating regimes in pulsed mode are accessible while keeping a minimum increase in temperature for the brain (0.5°C). This type of custom device represents a significant step forward for the optogenetics community, allowing multiple bright excitation sites along the length of a minimally invasive neural probe

Space charge in drift chambers operated with the Xe,CO2(15%) mixture

Using prototype modules of the ALICE Transition Radiation Detector we investigate space charge effects and the dependence of the pion rejection performance on the incident angle of the ionizing particle. The average pulse height distributions in the drift chambers operated with the Xe,CO2(15%) mixture provide quantitative information on the gas gain reduction due to space charge accumulating during the drift of the primary ionization. Our results demonstrate that the pion rejection performance of a TRD is better for tracks which are not at normal incidence to the anode wires. We present detailed simulations of detector signals, which reproduce the measurements and lend strong support to our interpretation of the measurements in terms of space charge effects.Comment: 18 pages, 10 figures, accepted for publication in Nucl.Instrum.Meth. A. Data files available at http://www-alice.gsi.de/tr

Ceramics studio to podiatry clinic: The impact of multi-media resources in the teaching of practical skills across diverse disciplines

This paper draws on the experiences of students from two vastly different disciplines to both explore the theoretical background supporting the use of multimedia resources to teach practical skills and provide a qualitative evaluation of student perceptions and experiences of using bespoke resources. Within ceramics and podiatry, practical skills are traditionally taught via an apprenticeship model within small groups. We explore the practical and pedagogic benefits of developing bespoke multimedia resources to teach practical skills, identifying common themes from these disparate discipline areas. Student focus groups revealed that, practically, the opportunity for repeated viewing at convenient times promoted less reliance on lecturers and better preparation prior to practical demonstrations. Pedagogically, time for reflection and sense making underpinned an increase in confidence which in turn led to increased creativity. The student voice was also used to identify recommendations and challenges driving future change

Sintering of calcium phosphates with a femtosecond pulsed laser for hard tissue engineering

The authors acknowledge support from the sponsors of this work; the EPSRC LUMIN (EP/K020234/1) and EU-Marie-Curie-IAPP LUSTRE (324538) projects.Direct laser sintering on hard tissues is likely to open new pathways for personalised medicine. To minimise irradiation damage of the surrounding soft tissues, lasers operating at wavelengths that are ‘safe’ for the tissues and biomaterials with improved optical properties are required. In this work laser sintering is demonstrated with the use of an ultrafast, femtosecond (100 fs) pulsed laser operating at a wavelength of 1045 nm and two existing calcium phosphate minerals (brushite and hydroxyapatite) which have been improved after doping with iron (10 mol%). Femtosecond laser irradiation caused transformation of the Fe3+-doped brushite and Fe3+-doped HAp samples into β-calcium pyrophosphate and calcium-iron-phosphate, respectively, with simultaneous evidence for microstructural sintering and densification. After estimating the temperature profile at the surface of the samples we suggest that soft tissues over 500 μm from the irradiated zone would be safe from thermal damage. This novel laser processing provides a means to control the phase constitution and the morphology of the finished surfaces. The porous structure of β-pyrophosphate might be suitable for applications in bone regeneration by supporting osteogenic cell activity while, the densified Fe3+-rich calcium-iron-phosphate may be promising for applications like dental enamel restoration.PostprintPeer reviewe