CEP-stable Tunable THz-Emission Originating from Laser-Waveform-Controlled Sub-Cycle Plasma-Electron Bursts

We study THz-emission from a plasma driven by an incommensurate-frequency two-colour laser field. A semi-classical transient electron current model is derived from a fully quantum-mechanical description of the emission process in terms of sub-cycle field-ionization followed by continuum-continuum electron transitions. For the experiment, a CEP-locked laser and a near-degenerate optical parametric amplifier are used to produce two-colour pulses that consist of the fundamental and its near-half frequency. By choosing two incommensurate frequencies, the frequency of the CEP-stable THz-emission can be continuously tuned into the mid-IR range. This measured frequency dependence of the THz-emission is found to be consistent with the semi-classical transient electron current model, similar to the Brunel mechanism of harmonic generation

Precision public health – A critical review of the opportunities and obstacles

The term ‘precision public health’ (PPH) refers to a new approach in public health which involves the use of novel data sources and/or computer science-driven methods of data analysis to predict risk or outcomes, in order to improve how interventions are targeted or tailored, with the aim of making them more individualised and therefore more effective and cost-effective than methods currently in use. These data may include, for example, information from social media or devices, genomic or clinical data, and information from healthcare services. In this critical review, which was conducted between March and October 2019, we outline key assumptions underpinning the PPH approach and identify potential challenges in its application. We adopted a pragmatic, non-systematic review methodology to examine: (i) the general principles underlying PPH; (ii) the validity of claims made about PPH in empirical studies and commentaries; and (iii) the potential opportunities and challenges of adopting a PPH approach through examining two case studies: health checks and community-based interventions. Non-empirical studies (commentaries and think-pieces) were included in this review because PPH represents an emerging approach and many of the ideas around the potential of PPH are only described in such studies Commentary studies emphasise that precision can be achieved in targeting interventions towards narrow social profiles of people through the incorporation of data reflecting micro-level day-to-day insights into the lives of individuals. Structured analysis of commentary studies shows that (i) the PPH field may be highly influenced by commentary and non-systematic review pieces that lack transparent methods but make claims about the potential of PPH; (ii) commentators on PPH often attempt to provide evidence for claims but the link between the evidence and the claim is often unsubstantiated when critically examined; and (iii) many of the assumptions underlying PPH are not supported by empirical evidence suggesting that there needs to be a measured approach to adopting PPH approaches. Claims around the effectiveness of PPH and around PPH being an advance on current public health approaches tended not to be supported by empirical evidence. As a relatively new concept therefore, there is limited direct empirical evidence showing PPH to be effective, and the theoretical arguments in its favour are often not well supported by evidence. The more ambitious claims made for PPH in the literature often rest on questionable readings of the evidence – for example, citing the possibility of identifying subgroups of the population through better targeting as though this automatically promises greater effectiveness among interventions targeting those subgroups. In practice, it seems that PPH is less a radically new paradigm and more a range of incremental improvements to public health interventions. Hypothetical case studies outlining the potential of a PPH approach applied to health checks and community-based interventions indicate several ways in which new data or tools could be productively used to inform the design and implementation of public health interventions. Current evidence suggests the impact of these is likely to be fairly modest, although further focused research (e.g. exploring the utility of strategies for targeting or involving communities using PPH) may merit further exploration and evaluation. Defining PPH is contentious and our findings reflect the difficulty in assessing and operationalising the broad ambition of using emerging data and technologies to better understand profiles, predict risk and outcomes, and act upon this evidence. Future work in this area should seek to introduce more focus around the concept of PPH, including being clearer about the goals and breaking down the concept into a series of components that can each be evaluated. The bulk of the work presented here took place between March and October 2019. There is scope for further analysis to understand the potential of PPH in the future, as the number of studies adopting a PPH approach grows. This larger pool of studies may also lend itself to more systematic approaches to reviewing the evidence, particularly if there is an interest in evaluating a particular component or principle of PPH. In addition, the evidence examined in this report predates the COVID-19 global pandemic, and many of the measures taken to mitigate the spread of the pandemic may provide a further source of evidence and data to understand the potential role of PPH in public health decision-making

Hidridna redukcija B-norholestan 5α,6α-epoksida

B-Norcholestane epoxide 2 is reduced with lithium aluminium hydride to give either the 3β,6α-diol 3 or the corresponding 3β,5α-diol 4, depending on the quality of the reducing reagent employed. Aplausible mechanistic explanation of the obtained results is suggested.Redukcijom B-norholestan-epoksida 2 pomoću litijum-aluminijum-hidrida dobijeni su odgovarajući 3β,6α-diol 3 ili 3β,5α-diol 4, u zavisnosti od kvaliteta upotrebljenog redukcionog reagensa. Predloženo je verovatno mehanističko tumačenje dobijenih rezultata

Little groups of irreps of O(3), SO(3), and the infinite axial subgroups

Little groups are enumerated for the irreps and their components in any basis of O(3) and SO(3) up to rank 9, and for all irreps of C$_{\infty}$, C$_{\infty h}$, C$_{\infty v}$, D$_{\infty}$ and D$_{\infty h}$. The results are obtained by a new chain criterion, which distinguishes massive (rotationally inequivalent) irrep basis functions and allows for multiple branching paths, and are verified by inspection. These results are relevant to the determination of the symmetry of a material from its linear and nonlinear optical properties and to the choices of order parameters for symmetry breaking in liquid crystals.Comment: 28 pages and 3 figure

Hepatocyte growth factor is upregulated in ischemic retina and contributes to retinal vascular leakage and neovascularization

In patients with macular edema due to ischemic retinopathy, aqueous levels of hepatocyte growth factor (HGF) correlate with edema severity. We tested whether HGF expression and activity in mice with oxygen-induced ischemic retinopathy supports a role in macular edema. In ischemic retina, HGF was increased in endogenous cells and macrophages associated with retinal neovascularization (NV). HGF activator was increased in and around retinal vessels potentially providing vascular targeting. One day after intravitreous injection of HGF, VE-cadherin was reduced and albumin levels in retina and vitreous were significantly increased indicating vascular leakage. Injection of VEGF caused higher levels of vitreous albumin than HGF, and co-injection of both growth factors caused significantly higher levels than either alone. HGF increased the number of macrophages on the retinal surface, which was blocked by anti-c-Met and abrogated in chemokine (C-C motif) ligand 2 (CCL2)−/− mice. Injection of anti-c-Met significantly decreased leakage within 24 hours and after 5 days it reduced retinal NV in mice with ischemic retinopathy, but had no effect on choroidal NV. These data indicate that HGF is a pro-permeability, pro-inflammatory, and pro-angiogenic factor and along with its activator is increased in ischemic retina providing support for a potential role of HGF in macular edema in ischemic retinopathies.Fil: Lorenc, Valeria Erika. Universidad Austral. Facultad de Ciencias Biomédicas. Instituto de Investigaciones en Medicina Traslacional. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones en Medicina Traslacional; Argentina. University Johns Hopkins; Estados UnidosFil: Lima e Silva, Raquel. University Johns Hopkins; Estados UnidosFil: Hackett, Sean F.. University Johns Hopkins; Estados UnidosFil: Fortmann, Seth D.. University Johns Hopkins; Estados UnidosFil: Liu, Yuanyuan. University Johns Hopkins; Estados UnidosFil: Campochiaro, Peter A.. University Johns Hopkins; Estados Unido

Oksidativne fragmentacije 5-hidroksi-1-okso-5α-holestan-3β-il-acetata

5-hydroxy-1-oxo-5α-cholestan-3β-yl acetate (11) was prepared in 5 steps starting from (E)-3β-acetoxy-5,10-seco-1(10)-cholesten-5-one (6). Treatment of the 1-oxo-5-hydroxy derivative 11 with lead tetraacetate (LTA) (under thermal or hypoiodite conditions) or with mercuric oxide/iodine (HgO/I2) reagent resulted in the oxidative β-fragmentation of the C(5)–C(10) bond affording 1,5-dioxo-5,10-secocholest-10(19)-en-3β-yl acetate (12), in different yields, depending on the reagent. Also the stereochemistry of the 1β,6β-cyclization product 13, formed by transannular cyclization of the 1,5-diketone 12 on silica gel, is discussed in this work.Sintetizovan je 5-hidroksi-1-okso-5α-holestan-3β-il-acetata (11) u 5 faza polazeći od (E)- 3β-acetoksi-5,10-seko-1(10)-holesten-5-ona (6). Dejstvom olovo-tetraacetata (LTA) (pod termičkim ili hipojoditnim uslovima), ili merkuri-oksid/jodnog reagensa (HgO/I2) na 1-okso-5-hidroksi derivat 11, vrši se oksidativna β-fragmentacija njegove C(5)–C(10) veze, pri čemu se dobija 1,5-diokso-5,10-sekoholest-10(19)-en-3β-il-acetat (12), u različitim prinosima u zavisnosti od upotrebljenog reagensa. Takođe, diskutovana je stereohemija 1β,6β-ciklizacionog proizvoda 13, nastalog intramolekulskom ciklizacijom 1,5-diokso-5,10-seko jedinjenja 12 na silika gelu

Biomechanics of predator–prey arms race in lion, zebra, cheetah and impala

The fastest and most manoeuvrable terrestrial animals are found in savannah habitats, where predators chase and capture running prey. Hunt outcome and success rate are critical to survival, so both predator and prey should evolve to be faster and/or more manoeuvrable. Here we compare locomotor characteristics in two pursuit predator–prey pairs, lion–zebra and cheetah–impala, in their natural savannah habitat in Botswana. We show that although cheetahs and impalas were universally more athletic than lions and zebras in terms of speed, acceleration and turning, within each predator–prey pair, the predators had 20% higher muscle fibre power than prey, 37% greater acceleration and 72% greater deceleration capacity than their prey. We simulated hunt dynamics with these data and showed that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival, and that the predator needs to be more athletic than its prey to sustain a viable success rate

Kiselo-katalizovana i fotolitička reaktivnost nekih nezasićenih B-nor-5,10-sekosteroidnih ketona

The acid-catalyzed reaction of (Z)- and (E)-B-nor-5,10-seco-ketones 2 and 3 resulted in an intramolecular cyclization to give the 5-hydroxy-A-nor-1β,5β-10(19)-methylidene derivative 8, the 5β-hydroxy-A-nor-1(10)-unsaturated compound 9 and the 5β,10β-dihydroxy A-nor-product 10, from the (Z)-isomer and the 5-hydroxy-A-nor-1β,5β-10(19)-methylidene product 11, from the (E)-isomer. Upon UV-irradiation, the (Z)- and (E)-seco-ketones 2 and 3 underwent a reversible (Z)/(E) and (E)/(Z)-isomerization and in addition to a transannular photocyclization to afford the 10(19)-methylidene derivatives 8 and 11, respectively, while photolysis of the 10(19)-methylidene-B-nor-5,10-seco-ketone 4 gave the oxetane derivative 12.Kiselo-katalizovana reakcija (Z)- i (E)-B-nor-5,10-seko-ketona 2 i 3 rezultuje u intramolekulskoj ciklizaciji dajući 5-hidroksi-A-nor-1β,5β-10(19)-metilidenski derivat 8, 5β-hidroksi A-nor-1(10)-nezasićeno jedinjenje 9 i 5β,10β-dihidroksi-A-nor-proizvod 10, iz Z-izomera, i 5-hidroksi-A-nor-1β,5β-10(19)-metilidenski proizvod 11, iz E-izomera. (Z)- i (E)-Seko- ketoni 2 i 3 UV-ozračivanjem podležu reverzibilnoj (Z)/(E) odnosno (E)/(Z) izomerizaciji, kao i transanularnoj fotociklizaciji dajući 10(19)-metilidenske derivate 8 odnosno 11, dok se fotolizom 10(19)-metilidenskog-5,10-seko-ketona 4 gradi oksetanski derivat 12

Out-of-equilibrium dynamics of photoexcited spin-state concentration waves

International audienceThe spin crossover compound [FeIIH2L2-Me][PF6]2 presents a two-step phase transition. In the intermediate phase, a spin state concentration wave (SSCW) appears resulting from a symmetry breaking (cell doubling) associated with a long-range order of alternating high and low spin molecular states. By combining time-resolved optical and X-ray diffraction measurements on a single crystal, we study how such a system responds to femtosecond laser excitation and we follow in real time the erasing and rewriting of the SSC