The reflectivity of relativistic ultra-thin electron layers

The coherent reflectivity of a dense, relativistic, ultra-thin electron layer is derived analytically for an obliquely incident probe beam. Results are obtained by two-fold Lorentz transformation. For the analytical treatment, a plane uniform electron layer is considered. All electrons move with uniform velocity under an angle to the normal direction of the plane; such electron motion corresponds to laser acceleration by direct action of the laser fields, as it is described in a companion paper. Electron density is chosen high enough to ensure that many electrons reside in a volume \lambda_R^3, where \lambda_R is the wavelength of the reflected light in the rest frame of the layer. Under these conditions, the probe light is back-scattered coherently and is directed close to the layer normal rather than the direction of electron velocity. An important consequence is that the Doppler shift is governed by \gamma_x=(1-(V_x/c)^2)^{-1/2} derived from the electron velocity component V_x in normal direction rather than the full \gamma-factor of the layer electrons.Comment: 7 pages, 4 figures, submitted to the special issue "Fundamental Physics with Ultra-High Fields" in The European Physical Journal

Routine production of 18F‾ with a beam current of 200 µA on a GE PETtrace cyclotron: Experience over > 18 Months

Introduction The increasing demand for [18F]FDG for clinical PET-CT and the efficiencies associated with large production runs have encouraged endeavors to increase the amount of 18F− produced by cyclotrons in a single run. The amount of 18F− is determined by the saturation yield of the nuclear reaction, the irradiation time and the beam current striking the target. The saturation yield is a function of beam energy (typically fixed for PET cyclotrons), the enrichment of the H218O (typically > 97 %) and the efficiency of the target design. Target design has already been optimized on current systems. Diminishing gains in activity are achieved by extending the irradiation time much beyond 3 hrs, so the main focus has been to increase beam current onto the targets. Increasing the beam current requires: i) a cyclotron capable of producing the increased beam current; ii) targets that tolerate the beam current without appreciable loss in saturation yield; iii) sufficient shielding of the cyclotron and hot cells to accommodate the proportionally larger radiation dose rates during higher current irradiation and from the larger activities delivered to the hot cells. We reported [1] that the self-shielded targets fitted to our cyclotron can accommodate 100 µA currents without appreciable loss in saturation yield. We also identified the potential of routine production at 200 A (100 A per target in dual target irradiation mode), but had not establish its long-term viability in routine use. We present our experience in using 200 µA for routine production of 18F- since September 2012. Material and Methods Our PETtrace cyclotron was installed in 2002 and has been used for routine production of various 18F and 11C tracers since January 2003. It has been upgraded incrementally so that it is now equivalent to a current generation PETtrace 880 cyclotron, which is specified at a total beam current of 130 µA. The only components on our cyclotron currently not part of the standard PETtrace 880 cyclotron configuration are the self-shielded targets and a license which allows total target beam current of 200 µA. The self-shielded targets utilize a W/Cu alloy for the main body of the target surrounding the Havar foil to provide shielding from the Havar foil by a factor of about 10 and shielding of any remnant 18F- activity in the targets by a factor of about 100 [1]. The niobium target chamber is the same size as used in the standard GE Nb25 targets. However, it dispenses with the He cooling and the vacuum foil. Only the water foil is used, which is directly exposed to the vacuum in the chamber. Foil cooling is through the water in the target chamber. One of the issues that we previously identified [1] is beam stripping by gas molecules in the vacuum tank. The amount of beam that is stripped and which impacts on components in the cyclotron is proportional to the beam current. At high currents, this can result in a runaway condition, where the effects of the stripped beam deteriorate vacuum; this then results in more beam stripping and more severe effects. The effect of diffusion pump maintenance on vacuum system performance and on the reduction of beam stripping was investigated as part of this study. We have previously found that running the ion source gas at a low flow rate (2 sccm) when cyclotron is not used greatly reduces deterioration of ion source performance over time and with use [1]. This gas flow also appears to have a beneficial effect on the vacuum. Ion source gas flow when cyclotron is off has been employed throughout the evaluation period. [18F]FDG was produced with TRACERlab MXFDG modules or FASTlab modules using both Phosphate and Citrate cassettes. Stability studies of [18F]FDG were performed to ensure it met specifications over the specified expiry time. Our current stabilization regime did not have to be adjusted for the higher activities produced with the higher beam currents. [18F]FDG yields were calculated using input activity estimates from saturation yield and beam time and current and the non-decay corrected [18F]FDG activity measured at the end of synthesis. Thus yield calculations include target yield variations and losses in the transfer lines and not just synthesis yield. Results and Conclusion The flip-in probe to extraction foil transmissions as a function of ion source gas flow are given in TABLE 1. Transmission decreases with increasing ion source gas flow, as expected for a system with an internal ion source. In addition, diffusion pump maintenance had a positive impact on the transmission and this is of particular benefit at the higher beam currents where minimising beam stripping becomes more critical. The ion source output, however, decreases with decreasing ion source gas flow; hence ion source gas flow is a compromise between ion source output and probe to foil transmission. We currently use a gas flow of 5.5 sccm for our 200 µA runs. Over the period from 1st September 2012 to end of March 2014, a total of 419 [18F]FDG produc-tions were performed at total target beam currents ranging from 160 µA to 200 µA, with 227 production runs being performed at 200 µA. Beam times were typically 90 to 120 min, with some productions up to 180 min. The [18F]FDG yields are summarized in TABLE 2. The yields for the FASTlab phosphate and citrate cassettes have been listed separately in TABLE 2 as they are known to be different [2,3]. The yields obtained with the TRACERlab MXFDG are also shown. The yields at 200 µA total target current are not appreciably different from those at 120 µAh, respectively. As more experience has been gained with the self-shielded targets, service interval is actually being extended from about 10,000 µAh to 20,000 µAh, despite the higher beam currents. Diffusion pump maintenance is currently recommended every 5 years, but a 2 year maintenance interval may be advantageous for 200 µA, given the observed deterioration over a 5 year period and the improvement in performance post service (Table 1). The more frequent service is associated with the additional costs of diffusion pump oil and an extra day of scheduled down-time. Typically, vacuum is sufficiently well established 24 h after opening of the vacuum tank to run 200 µA beams with the vacuum and beam conditioning that we employ. The targets generally have coped well with the 100 µA per target current (200 µA total beam current for dual target irradiation) over this 18 month period. However, currents of 80 µA to µ100 A per target in dual target irradiation mode reduce the tolerance to sudden increases in one of the target currents. There were 4 occasions (2 test beams and 2 production beams) when there were sudden increases of target current from 90 µA and 100 µA to about 150 µA. The rapid increase in heat deposited on the foil and target chamber and the resultant rapid pressure rise in the target chamber could not be withstood by the foil and target foil rupture ensued. This compared to 1 target foil issue over a similar period of time (18 months) at lower beam currents on the standard Nb25 target. Three separate causes were identified for these overshoots in target current: 1) behavior of control system when beam is allowed to continue past the set time; 2) large changes of set current of one of the two targets irradiated during a dual irradiation test beam and 3) an issue with DEE voltage regulation caused by the mechanical flap controls. These issues have been addressed by procedural changes (issues 1 and 2) and by fitting an available upgrade of the mechanical flap control mechanism (issue 3). The two target foil ruptures during production did not cause cancellation or delays to patient scanning, as the demand could be met by multi-ple productions and deliveries from the unaf-fected target. No unscheduled down-days occurred during the evaluation period. We have been able to achieve routine operation at 200 µA beam current through careful optimization of the critical components and parameters and a maintenance regime that we have detailed previously [1]. This maintenance scheme has not changed for the routine 200 µA operation. The safety margin, however, is reduced and so careful monitoring of the system is required to ensure that issues in one of the subsystems do not cause major events such as target foil ruptures. Our [18F]FDG yields have been maintained at the higher current and 200 µA allows large quantities of [18F]FDG to be produced routinely in a single run with relatively short beam times

Localization of a 64-kDa phosphoprotein in the lumen between the outer and inner envelopes of pea chloroplasts

The identification and localization of a marker protein for the intermembrane space between the outer and inner chloroplast envelopes is described. This 64-kDa protein is very rapidly labeled by [γ-32P]ATP at very low (30 nM) ATP concentrations and the phosphoryl group exhibits a high turnover rate. It was possible to establish the presence of the 64-kDa protein in this plastid compartment by using different chloroplast envelope separation and isolation techniques. In addition comparison of labeling kinetics by intact and hypotonically lysed pea chloroplasts support the localization of the 64-kDa protein in the intermembrane space. The 64-kDa protein was present and could be labeled in mixed envelope membranes isolated from hypotonically lysed plastids. Mixed envelope membranes incorporated high amounts of 32P from [γ-32P]ATP into the 64-kDa protein, whereas separated outer and inner envelope membranes did not show significant phosphorylation of this protein. Water/Triton X-114 phase partitioning demonstrated that the 64-kDa protein is a hydrophilic polypeptide. These findings suggest that the 64-kDa protein is a soluble protein trapped in the space between the inner and outer envelope membranes. After sonication of mixed envelope membranes, the 64-kDa protein was no longer present in the membrane fraction, but could be found in the supernatant after a 110000 × g centrifugation

Circulating adrenomedullin estimates survival and reversibility of organ failure in sepsis: the prospective observational multinational Adrenomedullin and Outcome in Sepsis and Septic Shock-1 (AdrenOSS-1) study

Background: Adrenomedullin (ADM) regulates vascular tone and endothelial permeability during sepsis. Levels of circulating biologically active ADM (bio-ADM) show an inverse relationship with blood pressure and a direct relationship with vasopressor requirement. In the present prospective observational multinational Adrenomedullin and Outcome in Sepsis and Septic Shock 1 (, AdrenOSS-1) study, we assessed relationships between circulating bio-ADM during the initial intensive care unit (ICU) stay and short-term outcome in order to eventually design a biomarker-guided randomized controlled trial. Methods: AdrenOSS-1 was a prospective observational multinational study. The primary outcome was 28-day mortality. Secondary outcomes included organ failure as defined by Sequential Organ Failure Assessment (SOFA) score, organ support with focus on vasopressor/inotropic use, and need for renal replacement therapy. AdrenOSS-1 included 583 patients admitted to the ICU with sepsis or septic shock. Results: Circulating bio-ADM levels were measured upon admission and at day 2. Median bio-ADM concentration upon admission was 80.5 pg/ml [IQR 41.5-148.1 pg/ml]. Initial SOFA score was 7 [IQR 5-10], and 28-day mortality was 22%. We found marked associations between bio-ADM upon admission and 28-day mortality (unadjusted standardized HR 2.3 [CI 1.9-2.9]; adjusted HR 1.6 [CI 1.1-2.5]) and between bio-ADM levels and SOFA score (p < 0.0001). Need of vasopressor/inotrope, renal replacement therapy, and positive fluid balance were more prevalent in patients with a bio-ADM > 70 pg/ml upon admission than in those with bio-ADM ≤ 70 pg/ml. In patients with bio-ADM > 70 pg/ml upon admission, decrease in bio-ADM below 70 pg/ml at day 2 was associated with recovery of organ function at day 7 and better 28-day outcome (9.5% mortality). By contrast, persistently elevated bio-ADM at day 2 was associated with prolonged organ dysfunction and high 28-day mortality (38.1% mortality, HR 4.9, 95% CI 2.5-9.8). Conclusions: AdrenOSS-1 shows that early levels and rapid changes in bio-ADM estimate short-term outcome in sepsis and septic shock. These data are the backbone of the design of the biomarker-guided AdrenOSS-2 trial. Trial registration: ClinicalTrials.gov, NCT02393781. Registered on March 19, 2015

New engineering approach for the development and demonstration of a multi-purpose platform for the Blue Growth Economy

Aquaculture is currently the fastest growing food sector in the world and the open oceans are seen as one of the most likely areas for large scale expansion [1], [2], [3]. The global demand for seafood is continuing to rise sharply, driven by both population growth and increased per capita consumption, whilst wild capture fisheries are constrained in their potential to produce more seafood. A recently funded EC project, the Blue Growth Farm BGF (GA n. 774426, 1st June 2018 ÷ 30th September 2021) aims at contributing to this world need with an original solution. The Blue Growth Farm proposes an efficient, cost competitive and environmentally friendly multi purpose offshore farm concept based on a modular floating structure, moored to the seabed, meeting requirements of efficiency, cost-competitiveness and environmental friendless, where automated aquaculture and renewable energy production systems are integrated and engineered for profitable applications in the open sea. In the present paper, the overall engineering approach developed to carry out the research work is presented, described and justified. Different technical and scientific challenges are addressed through an integrated industrial engineering design approach, where all disciplines are tuned to achieve the Blue Growth Farm main targets, represented by: i) guaranteeing expected nominal fish production thanks to advanced automation and remote control capabilities; ii) minimizing the pollution introduced at marine ecosystem level when exploiting the marine natural resources, whilst increasing the social acceptance and users community agreement; iii) maximizing the electricity production in the Blue Growth Farm potential installation area ecosystem to provide energy supply to the on board electrical equipment and to dispatch the extra produced electric energy to the land network. Preliminary engineering design results are promising to demonstrate effective increase of safety and efficiency by reducing on board human effort and consequently risks at offshore, thus to make commercial scale open ocean farming a reality

Formal Specification and Validation of Security Policies

International audienceWe propose a formal framework for the specification and validation of security policies. To model a secured system, the evolution of security information in the system is described by transitions triggered by authorization requests and the policy is given by a set of rules describing the way the corresponding decisions are taken. Policy rules are constrained rewrite rules whose constraints are first-order formulas on finite domains, which provides enhanced expressive power compared to classical security policy specification approaches like the ones using Datalog, for example. Our specifications have an operational semantics based on transition and rewriting systems and are thus executable. This framework also provides a common formalism to define, compare and compose security systems and policies. We define transformations over secured systems in order to perform validation of classical security properties

Forest biodiversity, ecosystem functioning and the provision of ecosystem services

Forests are critical habitats for biodiversity and they are also essential for the provision of a wide range of ecosystem services that are important to human well-being. There is increasing evidence that biodiversity contributes to forest ecosystem functioning and the provision of ecosystem services. Here we provide a review of forest ecosystem services including biomass production, habitat provisioning services, pollination, seed dispersal, resistance to wind storms, fire regulation and mitigation, pest regulation of native and invading insects, carbon sequestration, and cultural ecosystem services, in relation to forest type, structure and diversity. We also consider relationships between forest biodiversity and multifunctionality, and trade-offs among ecosystem services. We compare the concepts of ecosystem processes, functions and services to clarify their definitions. Our review of published studies indicates a lack of empirical studies that establish quantitative and causal relationships between forest biodiversity and many important ecosystem services. The literature is highly skewed; studies on provisioning of nutrition and energy, and on cultural services, delivered by mixed-species forests are under-represented. Planted forests offer ample opportunity for optimising their composition and diversity because replanting after harvesting is a recurring process. Planting mixed-species forests should be given more consideration as they are likely to provide a wider range of ecosystem services within the forest and for adjacent land uses. This review also serves as the introduction to this special issue of Biodiversity and Conservation on various aspects of forest biodiversity and ecosystem services

Sarcoma classification by DNA methylation profiling

Sarcomas are malignant soft tissue and bone tumours affecting adults, adolescents and children. They represent a morphologically heterogeneous class of tumours and some entities lack defining histopathological features. Therefore, the diagnosis of sarcomas is burdened with a high inter-observer variability and misclassification rate. Here, we demonstrate classification of soft tissue and bone tumours using a machine learning classifier algorithm based on array-generated DNA methylation data. This sarcoma classifier is trained using a dataset of 1077 methylation profiles from comprehensively pre-characterized cases comprising 62 tumour methylation classes constituting a broad range of soft tissue and bone sarcoma subtypes across the entire age spectrum. The performance is validated in a cohort of 428 sarcomatous tumours, of which 322 cases were classified by the sarcoma classifier. Our results demonstrate the potential of the DNA methylation-based sarcoma classification for research and future diagnostic applications