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The ability to predict heavy rain and floods in Africa is urgently needed to reduce the socioeconomic costs of these events and increase resilience as climate changes. Numerical weather prediction in this region is challenging, and attention is being drawn to observationally based methods of providing short-term nowcasts (up to ∼6-h lead time). In this paper a freely available nowcasting package, pySTEPS, is used to assess the potential to provide nowcasts of satellite-derived convective rain rate for West Africa. By analyzing a large number of nowcasts, we demonstrate that a simple approach of “optical flow” can have useful skill at 2-h lead time on a 10-km scale and 4-h lead time at larger scales (200 km). A diurnal variation in nowcast skill is observed, with the worst-performing nowcasts being those that are initialized at 1500 UTC. Comparison with existing nowcasts is presented. Such nowcasts, if implemented operationally, would be expected to have significant benefits. Significance Statement A freely available, easy-to-use nowcasting package has been applied to satellite-retrieved rainfall rates for West Africa, and extrapolations have useful skill at up to 4 h of lead time.

In social groups, disease risk is not distributed evenly across group members. Individual behaviour is a key source of variation in infection risk, yet its effects are difficult to separate from those of other factors. Here, we combine long-term epidemiological experiments and automated tracking in clonal raider ant colonies, where behavioural individuality emerges among identical workers. We find that: 1) division of labour determines the distribution of parasitic nematodes (Diploscapter) among hosts, showing that differences in infection can emerge from behavioural variation alone, 2) infections affect colony social organisation by causing infected workers to stay in the nest. By disproportionally infecting some workers and shifting their spatial distribution, infections reduce division of labour and increase spatial overlap between hosts, which is expected to facilitate parasite transmission. Thus, division of labour, a defining feature of many societies, not only shapes infection risk and distribution but can also be modified by parasites.

Utilising a combination of experimental results obtained via positron emission particle tracking (PEPT) and numerical simulations, we study the influence of a system’s geometric and elastic properties on the convective behaviours of a dilute, vibrofluidised granular assembly. Through the use of a novel, ‘modular’ system geometry, we demonstrate the existence of several previously undocumented convection-inducing mechanisms and compare their relative strengths across a broad, multi-dimensional parameter space, providing criteria through which the dominant mechanism within a given system – and hence its expected dynamics – may be predicted. We demonstrate a range of manners through which the manipulation of a system’s geometry, material properties and imposed motion may be exploited in order to induce, suppress, strengthen, weaken or even invert granular convection. The sum of our results demonstrates that boundary-layer effects due to wall (in)elasticity or directional impulses due to ‘rough’ boundaries exert only a secondary influence on the system’s behaviour. Rather, the direction and strength of convective motion is predominantly determined by the energy flux in the vicinity of the system’s lateral boundaries, demonstrating unequivocally that pseudo-thermal granular convection is decidedly a collective phenomenon.

International audience; This article explores the contrasting reactivity of cyclopropyl complexes of early transition metals. [Cp*W(NO)(CH2R)(c‐C3H5)] (R = SiMe3, Ph, t‐Bu) generated in THF solution from [Cp*W(NO)(CH2R)Cl] and [Mg(c‐C3H5)2(dioxane)x] readily rearrange to η3‐allyl derivatives [Cp*W(NO)(CH2R)(η3‐C3H5)] by an intramolecular ring opening reaction. Both direct and catalyzed pathways are revealed by kinetic studies. Computational modeling indicates the ring opening reaction is preferred on thermodynamic grounds for tungsten whereas kinetic products arising from β‐H abstraction reactions of cyclopropane are observed for related zirconium and niobium complexes reported previously. The energetic accessibility and the nature of the LUMO in the tungsten complexes promote distal CC bond cleavage in the cyclopropyl ring.

International audience; In an effort to study the β-H abstraction/1,3-addition mechanism for CH bond activation, the syntheses of tungsten organometallic complexes featuring a cyclopropyl ligand were undertaken. Attempts to prepare the chloro cyclopropyl complex Cp*W(NO)Cl(c-C3H5) instead afforded the previously reported allyl complex Cp*W(NO)Cl(η3-CH2CHCH2), due to a ring-opening rearrangement of the cyclopropyl ligand. The alkyl cyclopropyl complex Cp*W(NO)(CH2SiMe3)(c-C3H5) (1TMS) was prepared and characterized in solution via NMR spectroscopy but also undergoes a ligand rearrangement process to afford the allyl complex Cp*W(NO)(CH2SiMe3)(η3-CH2CHCH2) (2TMS), which was characterized by NMR spectroscopy and an X-ray diffraction study. Attempts to inhibit the ligand rearrangement or isolate 1TMS in the solid state have been unsuccessful. In order to investigate the mechanism of the conversion of 1TMS to 2TMS, a kinetic study was undertaken, and some preliminary results are discussed.

The synthesis, characterization, and reactivity with H2 of a series of tantalum hydrocarbyl complexes are reported. The reaction of [NPN*]TaMe3 (4, where NPN* = PhP(2-(N-mesityl)-5-Me-C6H3)2) with dihydrogen (H2, 4 atm) results in the formation of the dinuclear tetrahydride ([NPN*]Ta)2(μ-H)4 (5), without the observation of intermediates. The preparations of two alkyne benzyl complexes of the formula [NPN*]Ta(alkyne)(CH2Ph) (where alkyne = BTA = bis(trimethylsilyl)acetylene (6), 3-hexyne (7)) are reported starting from the respective chloroalkyne complexes [NPN*]Ta(alkyne)Cl, by addition of benzylpotassium. Hydrogenation of these two alkyne benzyl complexes ultimately results in the formation of the same dinuclear tetrahydride 5; however, using lower pressures of H2 and shorter reaction times results in the isolation of an intermediate in each case. Hydrogenation of 6 generates the alkene hydride complex [NPN*]Ta(trans-1,2-C2H2(SiMe3)2)H (8); addition of H2 to 7 gives [NPN*]Ta(1-hexene)H (9), in which the ...

This review focuses on niobium and tantalum organometallic complexes that feature a metal-bound alkyne (RC≡CR) unit. The contrasting MIII–alkyne/MV–“alkenediyl” bonding motifs used to describe the metal–ligand interaction in these complexes are discussed. An overview of the spectroscopic and crystallographic structural metrics that are used to characterize alkyne complexes is also included. The various routes employed for the synthesis of tantalum and niobium alkyne complexes are summarized, and the reactivity of these complexes, including potential synthetic applications, is also addressed.

In the EarthCARE mission the BBR (Broad Band Radiometer) has the role of measuring the net earth radiance (i.e. total reflected-solar and thermally-emitted radiances), from the same earth scene as viewed by the other instruments (aerosol lidar, cloud radar and spectral imager). It does this measurement at 10km scene size and in 3 view angles. It is an imaging radiometer in that it uses micro-bolometer linear-array detector (pushbroom orientation), to over-sample these required scenes, with the samples being binned on-ground to produce the 10km radiance data. For the measurements of total earth radiance, the BBR is based on the heritage of Earth Radiation Budget (ERB) instruments. The ground calibration methods of this type of sensor is technically very similar to other EO instruments that measure in the thermalIR, but with added challenges: (1) The thermal-IR measurement has to have a much wider spectral range than normal thermal-IR channels to cover the whole earth-emission spectrum i.e. ~4 to >50microns; (2) The 2nd channel (reflected solar radiance) must also have a broad response to cover almost the whole solar spectrum, i.e. ~0.3 to 4microns. And this solar channel must be measured on the same radiometric calibration as the thermal channel, which in practice is best done by using the same radiometer for both channels. The radiometer is designed to be very broad-band i.e. 0.3 to 50microns (i.e. more than two decades), to cover both ranges, and a switchable spectral filter (short-pass cutoff at 4μm) is used to separate the channels. The on-ground measurements which are required to link the calibration of these channels will be described. A calibration of absolute responsivity in each of the two bands is needed; in the thermal-IR channel this is by the normal method of using a calibrated blackbody test source, and in the solar channel it is by means of a narrow-band (laser) and a reference radiometer (from NPL). A calibration of relative spectral response is also needed, across this wide range, for the purpose of linking the two channels, and for converting the narrow-band solar channel measurement to broad-band.

Excited states in certain atomic nuclei possess an unusual structure, where the dominant degrees of freedom are those of α clusters rather than individual nucleons. It has been proposed that the diffuse 3α system of the ^{12}C Hoyle state may behave like a Bose-Einstein condensate, where the α clusters maintain their bosonic identities. By measuring the decay of the Hoyle state into three α particles, we obtained an upper limit for the rare direct 3α decay branch of 0.047%. This value is now at a level comparable with theoretical predictions and could be a sensitive probe of the structure of this state.

The incorporation of o-phenylene-linked diamidophosphine ligands onto the readily available alkyne complexes Ta(alkyne)Cl3(DME) (where alkyne = hex-3-yne or 1,2-bis(trimethylsilylacetylene); DME = 1,2-dimethoxyethane) results in the formation of a versatile set of starting materials of the general formula [PhNPN*]Ta(alkyne)Cl (where [PhNPN*] = PhP(2-(N-mesityl)-5-Me-C6H3)2). Upon reaction with KBEt3H, the synthesis of the corresponding hydride complexes [PhNPN*]Ta(alkyne)H can be achieved; these complexes feature extremely downfield (δ ∼21 ppm) doublet resonances (2JHP = ∼35 Hz) in the respective 1H NMR spectra that are assigned to the newly formed Ta–H moieties. Subsequent reaction of these Ta hydrides with 2,6-dimethylphenylisocyanide and phenylacetylene results in the insertion of these species into the Ta–H bond and the formation of the corresponding iminoformyl and phenylvinyl complexes, respectively. While the former intermediate cannot be detected, the latter was characterized by NMR spectroscopy. ...

Positron emission particle tracking (PEPT) is a technique by which particle behaviour can be measured in a system of flow. The quality of the measurement is related to the spatial and temporal precision of the PET scanner and the characteristics of the tracer, which must replicate physical and chemical properties of the system bulk. Tracer particles can be made from ion exchange resins which have a high capacity for the commonly used positron emitting radionuclides 18F or 68Ga. However, these resins have a polymer composition and are naturally hydrophilic, which limits their application in systems involving mineral particles. This work presents a method to modify ion exchange resins with a coating to change the physical properties of the tracer. Two types of tracer were fabricated in this way, with hydrophobic and hydrophilic surfaces, to investigate the behaviour of valuable and gangue minerals in froth flotation with PEPT. The PEPT data were used to determine the spatial occupancies of each tracer, showing that the hydrophobic tracer has the highest occupancy in the froth region and the hydrophilic tracer is rarely entrained.

Study on translational and rotational motion of solids is important in a wide range of engineering processes. However, rotational motion of solid particles in an opaque system has not been given much attention due to the lack of appropriate measurement methods. This paper presents a new technique, Multiple-Positron Emission Particle Tracking (Multiple-PEPT), to track both rotational and translational motions of a solid simultaneously. The sample study presented here is to track the rotation and translation of a cubed potato in a food can for optimising the canned food process. The results have demonstrated that the rotational and transitional motion of the cubed potato can be simultaneously tracked through mounting three small (200 microns) radioactive tracers on the cube corners. The rotation and translation of the cube can be reconstructed based on the trajectories of the three tracers. The translational and rotational motions of the potato particle are related to each other, and both the motions are greatly dependent on the solids fraction, the liquid viscosity and the density difference between the solid and liquid; but follow specific patterns. (C) 2014 Elsevier Ltd. All rights reserved.

Radiography and tomography using proton beams promise benefit to image guidance and treatment planning for proton therapy. A novel proton tracking detector is described and experimental demonstrations at a therapy facility are reported. A new type of proton CT reconstructing relative "scattering power" rather than "stopping power" is also demonstrated. Notably, this new type of imaging does not require the measurement of the residual energies of the protons.A large area, silicon microstrip tracker with high spatial and temporal resolution has been developed by the Proton Radiotherapy Verification and Dosimetry Applications consortium and commissioned using beams of protons at iThemba LABS, Medical Radiation Department, South Africa. The tracker comprises twelve planes of silicon developed using technology from high energy physics with each plane having an active area of ∼10 × 10 cm segmented into 2048 microstrips. The tracker is organized into four separate units each containing three detectors at 60° to one another creating an x-u-v coordinate system. Pairs of tracking units are used to reconstruct vertices for protons entering and exiting a phantom containing tissue equivalent inserts. By measuring the position and direction of each proton before and after the phantom, the nonlinear path for each proton through an object can be reconstructed.Experimental results are reported for tracking the path of protons with initial energies of 125 and 191 MeV. A spherical phantom of 75 mm diameter was imaged by positioning it between the entrance and exit detectors of the tracker. Positions and directions of individual protons were used to create angular distributions and 2D fluence maps of the beam. These results were acquired for 36 equally spaced projections spanning 180°, allowing, for the first time, an experimental CT image based upon the relative scattering power of protons to be reconstructed.Successful tracking of protons through a thick target (phantom) has demonstrated that the tracker discussed in this paper can provide the precise directional information needed to perform proton radiography and tomography. When synchronized with a range telescope, this could enable the reconstruction of proton CT images of stopping power. Furthermore, by measuring the deflection of many protons through a phantom, it was demonstrated that it is possible to reconstruct a new kind of CT image (scattering power) based upon this tracking information alone.

Knowledge of solid motions and flow structures in fluidized beds is of significant importance to a number of industrial processes, such as combustion, gasification of solid fuels, drying of particulate materials, oxidation or reduction of ores, and catalytic and thermal cracking. Many parameters, such as pressure drop, bed geometry, solid size and density, can affect the solid flow structure in a fluidized bed. In this study, experiments were designed to investigate the impact of solid size. Through PEPT studies, we found that the solid flow structure and the bubble pattern in a fluidized bed with an inner diameter of 150 mm vary significantly with solid particle size. Three flow structures have been found. For glass beads with a large size (> 700 μm), a single large circulation cell is observed within the whole bed, and particles move upwards at one side of the bed to the splash zone, and then return to the bed bottom along the opposite side of the bed. When the particle size is in the range 250–450 μm, particles move upwards across the whole area of the bed at relatively uniform velocity in a layer 30 mm deep immediately above the air distributor. Above this layer, solids move inwards and travel upwards in the centre of the bed to the splash zone, and then return to the bottom of the bed in an outer annulus. When the particle size is in the range 80–200 μm, the fluidized bed can be divided into three sections. In the bottom section, solids travel upwards in the outer annulus, and move down in the bed centre. In the top section, solids travel upwards at the centre of the bed to the splash zone and then return to the intermediate height of the bed via the outer annulus. In the intermediate section of the bed (60–100 mm above the distributor), the annular upward solid flow from the bottom section encounters the annular downward flow from the top section. The two solid flows merge and change direction towards the bed centre where the particles are mixed and redistributed to the circulation cells in the upper and lower sections. The bubbling pattern also varies with the particle size. The bubble size and their rising velocity decrease with decreasing of the particle size.

Invasive alien species (IAS) cause major economic losses and threaten biodiversity worldwide. Taxonomic information is essential to initiating defence against IAS, including early detection and identification of new IAS outbreaks. We demonstrate how current IAS strategies (i.e. prevention of new invasions, early detection and rapid response to new invaders and management of established invaders) require strong taxonomic infrastructure. Examples are given from terrestrial molluscs (Gastropoda) and insects such as the Gypsy Moth, Lymantria dispar Linnaeus (Lepidoptera: Lymantriidae), disease vector flies of the families Culicidae and Calliphoridae (Diptera:), Sirex noctilio (Fabricius) (Hymenoptera: Siricidae) woodwasps and Dendroctonus bark beetles and the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), that demonstrate the role of taxonomy in IAS response. Further, we show through the example of the Emerald Ash Borer, Agrilus planipennis Fairmaire (Coleopte...

This review focuses on niobium and tantalum organometallic complexes that feature a metal-bound alkyne (RC≡CR) unit. The contrasting MIII–alkyne/MV–“alkenediyl” bonding motifs used to describe the metal–ligand interaction in these complexes are discussed. An overview of the spectroscopic and crystallographic structural metrics that are used to characterize alkyne complexes is also included. The various routes employed for the synthesis of tantalum and niobium alkyne complexes are summarized, and the reactivity of these complexes, including potential synthetic applications, is also addressed.

Using discrete particle simulations validated by experimental data acquired using the positron emission particle tracking technique, we study the efficiency of energy transfer from a vibrating wall to a system of discrete, macroscopic particles. We demonstrate that even for a fixed input energy from the wall, energy conveyed to the granular system under excitation may vary significantly dependent on the frequency and amplitude of the driving oscillations. We investigate the manner in which the efficiency with which energy is transferred to the system depends on the system variables and determine the key control parameters governing the optimization of this energy transfer. A mechanism capable of explaining our results is proposed, and the implications of our findings in the research field of granular dynamics as well as their possible utilization in industrial applications are discussed.

Controlling segregation is both a practical and a theoretical challenge. Using a novel drum design comprising concave and convex geometry, we explore, through the application of both discrete particle simulations and positron emission particle tracking, a means by which radial size segregation may be used to drive axial segregation, resulting in an order of magnitude increase in the rate of separation. The inhomogeneous drum geometry explored also allows the direction of axial segregation within a binary granular bed to be controlled, with a stable, two-band segregation pattern being reliably and reproducibly imposed on the bed for a variety of differing system parameters. This strong banding is observed to persist even in systems that are highly constrained in the axial direction, where such segregation would not normally occur. These findings, and the explanations provided of their underlying mechanisms, could lead to radical new designs for a broad range of particle processing applications but also may potentially prove useful for medical and microflow applications.

The behaviors of granular systems are sensitive to a wide variety of particle properties, including size, density, elasticity, and shape. Differences in any of these properties between particles in a granular mixture may lead to segregation, or "demixing," a process of great industrial relevance. Despite the known influence of particle geometry in granular systems, a considerable fraction of research into these systems concerns only uniformly spherical particles. We address, for the case of vertically vibrated granular systems, the important question of whether the introduction of differing particle geometries entirely invalidates our existing knowledge based on purely spherical granulates, or whether current models may simply be adapted to account for the effects of particle shape. We demonstrate that while shape effects can indeed influence the dynamical and segregative behaviors of a granular system, the segregative mechanisms associated with particle geometry are decidedly secondary to those related to particle density. The relevant control parameters determining the extent of geometrically induced segregation are established. Finally, a manner in which shape effects may be accounted for in simulations utilizing purely spherical particles is proposed.

Low-frequency oscillations (LFOs) are thought to play an important role in the transition between the Leidenfrost and convective states of a vibrated granular bed. This work details the experimental observation of LFOs, which are found to be consistently present for a range of driving frequencies and amplitudes, with particles of varying material and using containers of differing material properties. The experimentally acquired results show a close qualitative and quantitative agreement with both theory and simulations across the range of parameters tested. Strong agreement between experimental and simulation results was also observed when investigating the influence of sidewall dissipation on LFOs and vertical density profiles. This paper additionally provides evidence of two phenomena present in the Leidenfrost state: a circulatory motion over extended time periods in near-crystalline configurations, and a Leidenfrost-like state in which the dense upper region displays an unusual inverse thermal convection.

The transport properties of a natural fracture crossing a limestone block of 36 cm × 26 cm × 60 cm is studied using positron emission projection imaging. This non-invasive technique allows to measure the spatial distribution of the activity of a radioactive solution (here irradiated-copper-EDTA solution) within the fracture. The fracture aperture is measured from the spatial distribution of the activity as the fracture is completely filled with the tracer. The experiment consists in injecting the tracer at a constant flow rate in the plane of the fracture filled with an identical non-radioactive solution. Every 10 min, a two-dimensional grey scale image of the concentration field is recorded. The heterogeneity of the tracer distribution increases with time in relation with the spatial heterogeneity of the aperture field, and favours only slightly the region of larger aperture. The correlation length of the aperture distribution is larger than the correlation length of the concentration distribution of the tracer within the sample. Consequently, the concentration distribution cannot be modelled using a classical advection–dispersion equation; the mixing process has not reached a stationary Fickian dispersion regime in the finite size domain of the experiment. Nevertheless, the transversally averaged concentration profiles $$\overline c \left( x \right)$$ evaluated along the flow direction x rescale adequately with an advective variable $${x \mathord{\left/ {\vphantom {x {\overline U t}}} \right. \kern-\nulldelimiterspace} {\overline U t}} $$ , where $${\overline U }$$ is the mean velocity and t the time. This result is explained in the context of the geometrical dispersion regime where the mixing dispersion zone grows proportionally with time. Different approaches are proposed to characterise this anomalous dispersion regime.

著者人数：48名, Accepted: 2002-12-31, 資料番号: SA1002070000

The purpose of the D-CIXS (Demonstration of a Compact Imaging X-ray Spectrometer) instrument on the ESA SMART-1 mission is to provide high quality spectroscopic mapping of the Moon by imaging fluorescence X-rays emitted from the lunar surface. In order to obtain adequate statistics for what can be very weak sources, it is essential to have a large effective area, while maintaining a low mass. The solution is to make a thin, low profile detector, essentially a modern version of “X-ray detecting paper”. D-CIXS will achieve a spatial resolution on the ground of 42km from a spacecraft at 300 km altitude, with a spectral resolution of 200 eV or better. The instrument is based around the use of advanced dual microstructure collimator and Swept Charge Device X-ray detector technologies. Swept Charge Device X-ray detectors, a novel architecture based on proven CCD technology, have the virtue of providing superior X-ray detection and spectroscopic measurement capabilities, while also operating at room temperature. Thus we avoid the need for the large passive cooling radiator that was previously required to cool large X-ray focal plane CCDs. The advanced low profile microstructure collimation and filter design builds on expertise developed in solid state and microwave technology to enable us to dramatically reduce the instrument mass. The total mass of D-CIXS, including an X-ray solar monitor is ∼4.6 kg. D-CIXS will provide the first global map of the Moon in X-rays. During normal solar conditions, it will be able to detect absolute elemental abundances of Fe, Mg, Al and Si on the lunar surface, using the on-board solar monitor to obtain a continuous measurement of the input solar spectrum. During solar flare events, it will also be possible to detect other elements such as Ca, Ti, V, Cr, Mn, Co, K, P and Na. The global mapping of Mg, Al and Si, and in particular deriving Mg#, the magnesium number (MgO/[MgO+FeO]), represents the prime goal of the D-CIXS experiment.

Using a combination of experimental results acquired through positron emission particle tracking and simulational results obtained via the discrete particle method, we determine a scaling relationship for the center of mass height of a vibrofluidized three-dimensional, bidisperse granular system. We find the scaling to be dependent on the characteristic velocity with which the system is driven, the depth of the granular bed, and the elasticities of the particles involved, as well as the degree of segregation exhibited by the system and the ratio of masses between particle species. The scaling is observed to be robust over a significant range of system parameters.

We report a measurement of a new high spin Jπ=5- state at 22.4(2) MeV in 12C which fits very well to the predicted (ground state) rotational band of an oblate equilateral triangular spinning top with a D3h symmetry characterized by the sequence 0+, 2+, 3-, 4±, 5- with almost degenerate 4+ and 4- (parity doublet) states. Such a D3h symmetry was observed in triatomic molecules, and it is observed here for the first time in nuclear physics. We discuss a classification of other rotation-vibration bands in 12C such as the (0+) Hoyle band and the (1-) bending mode band and suggest measurements in search of the predicted ("missing") states that may shed new light on clustering in 12C and light nuclei. In particular, the observation (or nonobservation) of the predicted ("missing") states in the Hoyle band will allow us to conclude the geometrical arrangement of the three alpha particles composing the Hoyle state at 7.654 MeV in 12C.

Using a combination of experimental results and discrete particle method simulations, the role of buoyancy-driven convection in the segregative behavior of a three-dimensional, binary granular system is investigated. A relationship between convective motion and segregation intensity is presented, and a qualitative explanation for this behavior is proposed. This study also provides an insight into the role of diffusive behavior in the segregation of a granular bed in the convective regime. The results of this work strongly imply the possibility that, for an adequately fluidized granular bed, the degree of segregation may be indirectly controlled through the adjustment of the system's driving parameters, or the dissipative properties of the system's side-boundaries.

The heat transfer behaviour of the runout table operation has been modelled in the first stage of an investigation to quantify parameters affecting the final product quality of hot strip coil. The study has been carried out using the commercial software package ABAQUS/Standard, along with the available user routine capabilities. With the complex nature of heat removal during the process, emphasis is placed on the accurate description of the boundary conditions so as to achieve satisfactory temperature predictions. A preprocessor was developed to formulate actual plant data within the user routines, allowing the simulation of the accelerated cooling process according to particular cooling strategies as defined by the online control system. The model independently considers the geometrical position of the top and bottom laminar sprays and the calculation of the strip surface heat transfer coefficients at each time increment is achieved using boundary layer theory and an experimentally proven numeri...

This paper presents a new attenuation measurement technique suitable for rotating planar detector positron tomographs. Transmission measurements are made using two unshielded positron-emitting line sources, one attached to the front face of each detector. Many of the scattered and accidental coincidences are rejected by including only those coincidences that form a vector passing within a predetermined distance of either line source. Some scattered and accidental coincidences are still included, which reduces the measured linear attenuation: in principle their contribution can be accurately estimated and subtracted, but in practice, when limited statistics are available (as is the case with the multi-wire Birmingham positron camera), this background subtraction unacceptably increases the noise. Instead an attenuation image having the correct features can be reconstructed from the measured projections. For objects containing only a few discrete linear attenuation coefficients, segmentation of this attenuation image reduces noise and allows the correct linear attenuation coefficients to be restored by renormalization. Reprojection through the segmented image may then provide quantitatively correct attenuation correction factors of sufficient statistical quality to correct for attenuation in PET emission images.

The following recommendations are made: 1 Existing centres undertaking angioplasty should increase their activity, and the target figure of 400 PTCA procedures per million of the United Kingdom population should be achieved by the end of 1996-97, or immediately thereafter. 2 Angioplasty centres should be appropriately equipped to undertake PTCA safely and effectively and provide a reliable emergency service. They should have a minimum of two trained PTCA operators jointly undertaking a minimum of 200 procedures per year at that centre, and have regular meetings to share experience. 3 Angioplasty operators should ensure that where the need arises patients undergoing PTCA can receive immediate attention from a trained operator at any time until discharge from hospital. 4 Trained operators should undertake at least 1-2 PTCA procedures per week (> 60 procedures per year) to maintain competence, and those undertaking so few procedures should increase their activity over the next three years to more than 100 a year. 5 Trainers should have performed at least 500 procedures before formally training others and should undertake a minimum of 125 procedures a year to maintain accreditation as a trainer. 6 Surgical cover for PTCA procedures should be mandatory and on site cover remains the strongly preferred option. Where surgical cover is provided off site, this should be at a centre less than 30 minutes away by road. Whether provided on or off-site it should be possible to establish cardiopulmonary bypass within 90 minutes of the decision being made to refer the patient for surgery. 7 All operators and interventional centres should audit their activity and results, review these data locally with colleagues, and provide regular audit returns to the national database run by BCIS. This will allow future recommendations concerning standards to take more account of risk stratification and actual outcomes, and not place such emphasis merely on volumes of activity. 8 These recommendations should be reviewed in three years.

The Broadband Radiometer (BBR) is an instrument being developed for the ESA EarthCARE satellite. The BBR instrument is led by SEA in the UK with RAL responsible for the BBR optics unit (OU) while EADS Astrium is the EarthCARE prime contractor. The BBR detectors consist of three dedicated assemblies under the responsibility of INO. The detectors development started in 2008 and led to the design and implementation of a new gold black deposition facility at INO, in parallel with the preliminary and detailed design phases of the detector assemblies. As of today, two breadboard models and one engineering model have been delivered to RAL. The engineering qualification model manufacturing activities are on-going. This paper first provides an overview of the detectors assembly and principles of operation, with emphasis given to processes developed for the assembly and integration of the detectors. Detector-level qualification planning is finally discussed.