Quick X-ray microtomography using a laser-driven betatron source

Laser-driven X-ray sources are an emerging alternative to conventional X-ray tubes and synchrotron sources. We present results on microtomographic X-ray imaging of a cancellous human bone sample using synchrotron-like betatron radiation. The source is driven by a 100-TW-class titanium-sapphire laser system and delivers over $10^8$ X-ray photons per second. Compared to earlier studies, the acquisition time for an entire tomographic dataset has been reduced by more than an order of magnitude. Additionally, the reconstruction quality benefits from the use of statistical iterative reconstruction techniques. Depending on the desired resolution, tomographies are thereby acquired within minutes, which is an important milestone towards real-life applications of laser-plasma X-ray sources

Відкритість економік: фактори, показники та переваги

In de 'Kennismontage Hitte en Klimaat in de Stad' is een overzicht gemaakt van de huidige kennis rond de thema’s ‘stedelijk hitte-eiland’ en ‘hittestress’ relevant voor de uitvoeringspraktijk. De kennismontage is uitgevoerd door het Climate Proof Cities consortium in opdracht van de Alliantie Klimaatbestendige Steden, een samenwerkingsverband tussen de vier grote steden (Amsterdam, Rotterdam, Den Haag en Utrecht) en het Ministerie van Infrastructuur en Milieu. De kennismontage dient als informatiebasis voor de gemeenteambtenaar die met het thema hitte in de stad aan de slag wil

Pareto Optimization of a Laser Wakefield Accelerator

Optimization of accelerator performance parameters is limited by numerous trade-offs and finding the appropriate balance between optimization goals for an unknown system is challenging to achieve. Here we show that multi-objective Bayesian optimization can map the solution space of a laser wakefield accelerator in a very sample-efficient way. Using a Gaussian mixture model, we isolate contributions related to an electron bunch at a certain energy and we observe that there exists a wide range of Pareto-optimal solutions that trade beam energy versus charge at similar laser-to-beam efficiency. However, many applications such as light sources require particle beams at a certain target energy. Once such a constraint is introduced we observe a direct trade-off between energy spread and accelerator efficiency. We furthermore demonstrate how specific solutions can be exploited using \emph{a posteriori} scalarization of the objectives, thereby efficiently splitting the exploration and exploitation phases

Гипотензивный эффект факоэмульсификации катаракты у больных с некомпенсированной первичной открытоугольной глаукомой

Нами було досліджено вплив факоемульсифікації катаракти з імплантацією інтраокулярної лінзи на внутришньоочний тиск (ВОТ). Обстежено та прооперовано 44 ока (36 людей) хворих на катаракту зпідвищеннимвнутриочним тиском, який тримався на тлі прийому двох чи більше гіпотензивних препаратах, та з відкритим кутом передньої камери.Очі були поділені на дві групи: у першу групу увійшли очі з псевдоесфоліативним синдромом, друга – без псевдо ексфоліацій. Більш виражене зниження внутрішньоочного тиску спостерігалося на очах з псевдоексфоліативним синдромом (32,4%) ніж на очах без нього (27,6%). В результаті проведеного лікування крім нормалізації офтальмотонуса вдалося зменшити кількість застосовуваних гіпотензивних препаратів або повністю відійти від них на оперованих очах.Факоемульсифікація катаракти є ефективною методикою нормалізації ВОТ у хворих з ПВКГ і катарактою та може рекомендуватися як метод першого вибору в тактиці лікування даної групи пацієнтів.We have investigated the effect of phacoemulsification of cataract with implantation of intraocular lenses on intraocular pressure (IOP). Examined and operated 44 eyes (36 patients) with cataract and high intraocular pressure, which was kept in the background taking two or more antihypertensive medications, and an open anterior chamber angle. Eyes were divided into two groups: first group included eyes with psevdoesfoliation syndrome, the second – with out pseudoeksfoliation. A marked reduction of intraocular pressure was observed in eyes with PEX syndrome (32.4%) thanineyeswithout (27.6%). As a result of treatment but normalization of IOP managed to reduce the number of antihypertensive drugs used or completely away from them on the operated eyes. Phacoemulsification of the cataract is an effective method of normalization of IOP in patients with POAG and cataract and be recommended as a method of first choice in tactics of treatment of this patient group

Light-Induced Mechanistic Divergence in Gold(I) Catalysis:Revisiting the Reactivity of Diazonium Salts

In a systematic study of the Au-catalyzed reaction of o-alkynylphenols with aryldiazonium salts, we find that essentially the same reaction conditions lead to a change in mechanism when a light source is applied. If the reaction is carried out at room temperature using a AuI catalyst, the diazonium salt undergoes electrophilic deauration of a vinyl AuI intermediate and provides access to substituted azobenzofurans. If the reaction mixture is irradiated with blue LED light, C−C bond formation due to N2-extrusion from the diazonium salt is realized selectively, using the same starting materials without the need for an additional photo(redox) catalyst under aerobic conditions. We report a series of experiments demonstrating that the same vinyl AuI intermediate is capable of producing the observed products under photolytic and thermal conditions. The finding that a vinyl AuI complex can directly, without the need for an additional photo(redox) catalyst, result in C−C bond formation under photolytic conditions is contrary to the proposed mechanistic pathways suggested in the literature till date and highlights that the role of oxidation state changes in photoredox catalysis involving Au is thus far only poorly understood and may hold surprises for the future. Computational results indicate that photochemical activation can occur directly from a donor–acceptor complex formed between the vinyl AuI intermediate and the diazonium salt

Séparations mécaniques fluide/solide

Licencedécantation gravitaire ; centrifugations (décantation centrifuge et cyclones) ; filtrations (sur support et en profondeur