High power targets for cyclotron production of 99mTc‡

Introduction Technetium-99m, supplied in the form of 99Mo/99mTc generators, is the most widely used radioisotope for nuclear medical imaging. The parent isotope 99Mo is currently produced in nuclear reactors. Recent disruptions in the 99Mo supply chain [1] prompted the development of methods for the direct accelerator-based production of 99mTc. Our approach involves the 100Mo(p,2n)99mTc reaction on isotopically enriched molybdenum using small medical cyclotrons (Ep ≤ 20 MeV), which is a viable method for the production of clinically useful quantities of 99mTc [2]. Multi-Curie production of 99mTc requires a 100Mo target capable of dissipating high beam intensities [3]. We have reported the fabrication of 100Mo targets of both small and large area tar-gets by electrophoretic deposition and subsequent sintering [4]. As part of our efforts to further enhance the performance of molybdenum targets at high beam currents, we have developed a novel target system (initially de-signed for the GE PETtrace cyclotron) based on a pressed and sintered 100Mo plate brazed onto a dispersion-strengthened copper backing. Materials and Methods In the first step, a molybdenum plate is produced similarly to the method described in [5] by compacting approximately 1.5 g of commercially available 100Mo powder using a cylindrical tool of 20 mm diameter. A pressure between 25 kN/cm2 and 250 kN/cm2 is applied by means of a hydraulic press. The pressed molybdenum plate is then sintered in a reducing atmosphere (Ar/2% H2) at 1,700 oC for five hours. The resulting 100Mo plates have about 90–95 % of the molybdenum bulk density. The 100Mo plate is furnace brazed at ~750 oC onto a backing manufactured from a disperse on strengthened copper composite (e.g. Glidcop AL-15) using a high temperature silver-copper brazing filler. This process yields a unique, mechanically and thermally robust target system for high beam power irradiation. Irradiations were performed on the GE PETtrace cyclotrons at LHRI and CPDC with 16.5 MeV protons and beam currents ≥ 100 µA. Targets were visually inspected after a 6 hour, 130 µA bombardment (2.73 kW/cm2, average) and were found fully intact. Up to 4.7 Ci of 99mTc have been produced to date. The saturated production yield remained constant between 2 hour and 6 hour irradiations. Results and Conclusion These results demonstrate that our brazed tar-get assembly can withstand high beam intensities for long irradiations without deterioration. Efforts are currently underway to determine maximum performance parameters

River histories : A thematic review

Peer reviewe

The Vegan Society and social movement professionalization, 1944–2017

In a qualitative content analysis of The Vegan Society’s quarterly publication, The Vegan, spanning 73 years and nearly 300 issues, the trajectory of one of the world’s most radical and compassionate counter cuisine collectives is presented and critically assessed. The Vegan Society’s history provides a case study on the ways in which social movements negotiate difference and conflict. Specifically, this article highlights the challenges of identity, professionalization, and factionalism across the 20th and 21st centuries. This research also puts into perspective the cultural impact that veganism has had on Western society, namely the dramatic increase in vegan consumers, vegan products, and the normalcy of vegan nutrition

Comparing anatomy, chemical composition, and water permeability of suberized organs in five plant species: wax makes the difference

AbstractMain conclusion The efficiency of suberized plant/environment interfaces as transpiration barriers is not established by the suberin polymer but by the wax molecules sorbed to the suberin polymer.Abstract Suberized cell walls formed as barriers at the plant/soil or plant/atmosphere interface in various plant organs (soil-grown roots, aerial roots, tubers, and bark) were enzymatically isolated from five different plant species (Clivia miniata, Monstera deliciosa, Solanum tuberosum, Manihot esculenta, and Malus domestica). Anatomy, chemical composition and efficiency as transpiration barriers (water loss in m s −1 ) of the different suberized cell wall samples were quantified.Results clearly indicated that there was no correlation between barrier properties of the suberized interfaces and the number of suberized cell layers, the amount of soluble wax and the amounts of suberin. Suberized interfaces of C. miniata roots, M. esculenta roots, and M. domestica bark periderms formed poor or hardly any transpiration barrier. Permeances varyingbetween 1.1 and 5.1 × 10 −8 ms −1 were very close to the permeance of water (7.4 × 10 −8 ms −1 ) evaporating from a water/ atmosphere interface. Suberized interfaces of aerial roots of M. deliciosa and tubers of S. tuberosum formed reasonable transpiration barriers with permeances varying between 7.4 × 10 −10 and 4.2 × 10 −9 m s −1 , which were similar to the upperrange of permeances measured with isolated cuticles (about 10 −9 ms −1 ). Upon wax extraction, permeances of M. deliciosa and S. tuberosum increased nearly tenfold, which proves the importance of wax establishing a transpiration barrier. Finally,highly opposite results obtained with M. esculenta and S. tuberosum periderms are discussed in relation to their agronomicalimportance for postharvest losses and tuber storage.Keywords Bark · Diffusion barrier · Periderm · Suberization · Storage root · Transpiration · Tuber · Water loss · Wa

Interaction of surfactants with Prunus laurocerasus leaf surfaces: time-dependent recovery of wetting contact angles depends on physico-chemical properties of surfactants

Abstract Background Surfactants are added to spray solutions because they significantly improve foliar uptake of active ingredients (AIs) into the leaves. It was intended to investigate whether surfactant solutions forming a dried deposit on Prunus leaf surfaces after they were sprayed, lead to structural and functional changes of the cuticle/atmosphere interface. This could potentially result in irreversibly enhanced leaf surface wetting, which should be of major disadvantage. Enhanced wetting could promote leaching of ions and promote leaf surface colonization with microorganisms. Results Prunus laurocerasus leaf surfaces were sprayed with aqueous solutions of non-ionic alcohol ethoxylates, a cationic, an anionic and one large polar surfactant. Directly after spraying and drying of the different surfactant solutions, wetting contact angles of deionized water (without surfactant) were significantly lower (between 6 and 54°) compared to wetting contact angles on untreated leaves (77°). Leaf surface wettability with deionized water was more pronounced with non-ionic alcohol ethoxylates (wetting contact angles ranging between 6 and 22°) compared to the other 3 surfactants (wetting contact angles ranging between 42 and 54°). Wetting contact angles of deionized water on leaf surfaces treated with non-ionic alcohol ethoxylates continuously increased again over time resulting in final wetting contact angles not different from untreated leaf surfaces. The time-dependent recovery of wetting contact angles was dependent on the degree of ethoxylation of the non-ionic alcohol ethoxylates. The wetting contact angle recovery rate was lower the higher the degree of ethoxylation of the alcohol ethoxylates was. With the cationic, anionic and large polar surfactant a recovery of wetting contact angles was not observed. In addition, on fully dehydrated and dead leaves wetting contact angle recovery was not observed for any of the tested surfactants after spraying and drying. Analytical determinations of the amounts of alcohol ethoxylates on the leaf surfaces after spraying and drying showed that amounts of alcohol ethoxylates decreased over time on the surface (24–72 h). Conclusion Our results indicate that non-ionic alcohol ethoxylates diffused within hours from the leaf surface into the leaf over time and thus fully disappeared from the leaf surface. This was not the case with the cationic, anionic and the large polar surfactants remaining on the leaf surface. Graphical Abstrac

Transcriptomic changes in barley leaves induced by alcohol ethoxylates indicate potential pathways of surfactant detoxification

Abstract Hardly anything is known regarding the detoxification of surfactants in crop plants, although they are frequently treated with agrochemical formulations. Therefore, we studied transcriptomic changes in barley leaves induced in response to spraying leaf surfaces with two alcohol ethoxylates (AEs). As model surfactants, we selected the monodisperse tetraethylene glycol monododecyl (C12E4) ether and the polydisperse BrijL4. Barley plants were harvested 8 h after spraying with a 0.1% surfactant solution and changes in gene expression were analysed by RNA-sequencing (RNA-Seq). Gene expression was significantly altered in response to both surfactants. With BrijL4 more genes (9724) were differentially expressed compared to C12E4 (6197). Gene families showing pronounced up-regulation were cytochrome P450 enzymes, monooxygenases, ABC-transporters, acetyl- and methyl- transferases, glutathione-S-transferases and glycosyltransferases. These specific changes in gene expression and the postulated function of the corresponding enzymes allowed hypothesizing three potential metabolic pathways of AE detoxification in barley leaves. (i) Up-regulation of P450 cytochrome oxidoreductases suggested a degradation of the lipophilic alkyl residue (dodecyl chain) of the AEs by ω- and β- oxidation. (ii) Alternatively, the polar PEG-chain of AEs could be degraded. (iii) Instead of surfactant degradation, a further pathway of detoxification could be the sequestration of AEs into the vacuole or the apoplast (cell wall). Thus, our results show that AEs lead to pronounced changes in the expression of genes coding for proteins potentially being involved in the detoxification of surfactants