A polynomial approach to the realization of J-lossless behaviours

In this paper, a class of behaviours known as J-lossless behaviours is introduced, where J is a symmetric two-variable polynomial matrix. For a certain J, it is shown that the resulting set of J-lossless behaviours are SISO behaviours such that for each of such behaviours, there exists a quadratic differential form which is positive for nonzero trajectories of the behaviour and whose derivative is equal to the product of the input variable and the derivative of the output variable. Earlier, Van der Schaft and Oeloff had considered a specific form of realization for such behaviours that plays an important role in their model reduction procedure. In our paper, we give a method of computation of a state space realization from a transfer function of such a behaviour in the same form as considered by Van der Schaft and Oeloff, using polynomial algebraic methods. Apart from being useful in enlarging the scope of the model reduction procedure of Van der Schaft and Oeloff, we show that our method of realization also has application in the synthesis of lossless mechanical systems with given transfer functions using springs and masses

A polynomial approach to the realization of J-lossless behaviors

We consider the problem of realizing lossless behaviours with respect to the supply rate equal to the scalar product of the input and of the derivative of the output variables. Using polynomial algebraic method we devise a realization procedure which, starting from an image representation, yields the same state representation used by van der Schaft and Oeloff in the context of model reduction. We also apply the insights derived from this realization procedure to the synthesis of lossless mechanical systems with given transfer functions using springs and masses

Origin of the thiopyrone CTP-431 “unexpectedly” isolated from the marine sponge Cacospongia mycofijiensis

An intriguing hypothesis that latrunculin A, a well-known natural product, might have undergone transformation into the unprecedented thiopyrone CTP-431 upon long-term storage in methanol is advanced. Thus opening of the hemiacetal of latrunculin A, followed by E1CB elimination, and dehydration would give a polyene that could undergo intramolecular Diels-Alder reaction, followed by methanolysis of the thiazolidinone ring and ring closure by intramolecular thiol addition to an enone. Experimental evidence that the novel thiazolidinone to thiopyrone rearrangement can occur is presented.The marine sponge Cacospongia mycofijiensis, found in the ocean surrounding Fiji, is a source of several polyketide natural products with interesting biological properties,1 including the tubulin binding macrolide fijianolide B (also known as laulimalide),2,3 the HIF1 signal inhibitor mycothiazole,4,5 and the macrolide latrunculins (Figure 1).6 The thiazolidinone-containing latruculins are of mixed polyketide synthesis (PKS) and non-ribosomal peptide synthesis (NRPS) origin, and latrunculin A 1 disrupts microfilament assembly to such an extent that it is the most widely used chemical tool to study actin binding

Stereoselective synthesis of highly substituted tetrahydrofurans by diverted carbene O–H insertion reaction

Copper or rhodium catalyzed reaction of diazocarbonyl compounds with β-hydroxyketones gives highly substituted tetrahydrofurans with excellent diastereoselectivity, under mild conditions, in a single step process that starts as a carbene O–H insertion reaction but is diverted by an intramolecular aldol reaction

Stereoselective synthesis of highly substituted tetrahydrofurans by diverted carbene O–H insertion reaction

Copper or rhodium catalyzed reaction of diazocarbonyl compounds with β-hydroxyketones gives highly substituted tetrahydrofurans with excellent diastereoselectivity, under mild conditions, in a single step process that starts as a carbene O–H insertion reaction but is diverted by an intramolecular aldol reaction

Nitrogen-bridged, natural product-like octahydrobenzofurans and octahydroindoles: scope and mechanism of bridge-forming reductive amination via caged heteroadamantanes

The biological significance of sp3-rich synthetic scaffolds with natural product-like features yet distinct global frameworks is being increasingly recognised in medicinal chemistry and biochemistry. Taking inspiration from the vast array of bioactive, bridged alkaloids, we report the synthesis of unique, densely functionalised tricyclic scaffolds based on nitrogen-bridged, octahydrobenzofurans and octahydroindoles. These heterocycle-rich frameworks were assembled by a one-pot, two-step bridge-forming reductive amination process, which was shown to proceed via caged, heteroadamantane intermediates that thermodynamically drive an exo–endo epimerisation, enabling intramolecular azaMichael addition over the concave face of the fused bicyclic precursors. In addition to evaluating the scope of this aza bridge-forming reaction, further stereochemical complexity was introduced by subsequent diastereoselective ketone reductions and other manipulations. Finally, strategic diversity points (amino, carboxy) were decorated with common medicinal chemistry fragments, providing a set of exemplar derivatives with Lipinski compliant physicochemical properties

Synthesis of toxyloxanthone B

A synthesis of the naturally occurring xanthone toxyloxanthone B is described, in which the key step is the regioselective addition of a methyl salicylate to a substituted benzyne followed by cyclization of the intermediate aryl anion to form the xanthone, the regiochemistry of the aryne addition being confirmed by X-ray crystallography. Subsequent introduction of the pyran ring by [3,3]-rearrangement and deprotection completed the synthesi

Decreased fertility rates in 9639 women diagnosed with inflammatory bowel disease: a United Kingdom population-based cohort study

Background: Clinical studies have reported reduced fertility in women with inflammatory bowel disease (IBD). Aim: To compare fertility rates in women with IBD to those in women without IBD and assess whether the relative fertility differed following IBD diagnosis, flares and surgery. Methods: Women aged 15-44 years in 1990-2010 were identified from a UK primary care database. We estimated overall and age-specific fertility rates by 5-year age bands for women with and without IBD. We used Poisson regression to calculate adjusted fertility rate ratios (AFRR), adjusted for age, smoking and socioeconomic deprivation. Results: There were 46.2 live births per 1000 person-years [95% confidence interval (95% CI); 44.6-47.9] in 9639 women with IBD and 49.3 (95% CI 49.2-49.5) in 2 131 864 without (AFRR: 0.93; 95% CI: 0.89-0.96). Excluding periods of contraception use, the AFRR was 0.99 (95% CI: 0.95-1.03). Before diagnosis, the AFRR for women with ulcerative colitis (UC) was 1.07 (95% CI: 0.99-1.16) and was 0.88 (95% CI: 0.81-0.97) for women with CD. After diagnosis, AFRRs were 0.87 (95% CI: 0.82-0.94) for CD and 0.92 (95% CI: 0.86-1.00) for UC. The fertility rate was lower following flares (AFRR: 0.70; 95% CI: 0.59-0.82) or surgery (AFRR: 0.84; 95% CI: 0.77-0.92). Women with pouch and non-pouch surgery had similar overall fertility though the reduction after surgery was greater for pouches (AFRR: 0.48; 95% CI: 0.23-0.99). Conclusions: Women with Crohn's disease have marginally lower fertility rates. These rates decreased following flares and surgical interventions. Fertility rates returned almost to normal when women were not prescribed contraception but the reduction following surgical intervention remained. As the lifetime effect of pouch vs. nonpouch surgery on fertility is small, the reduction post-pouch surgery should be interpreted with caution

Cavity-Enhanced 2D Material Quantum Emitters Deterministically Integrated with Silicon Nitride Microresonators

Optically active defects in 2D materials, such as hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDs), are an attractive class of single-photon emitters with high brightness, room-temperature operation, site-specific engineering of emitter arrays, and tunability with external strain and electric fields. In this work, we demonstrate a novel approach to precisely align and embed hBN and TMDs within background-free silicon nitride microring resonators. Through the Purcell effect, high-purity hBN emitters exhibit a cavity-enhanced spectral coupling efficiency up to $46\%$ at room temperature, which exceeds the theoretical limit for cavity-free waveguide-emitter coupling and previous demonstrations by nearly an order-of-magnitude. The devices are fabricated with a CMOS-compatible process and exhibit no degradation of the 2D material optical properties, robustness to thermal annealing, and 100 nm positioning accuracy of quantum emitters within single-mode waveguides, opening a path for scalable quantum photonic chips with on-demand single-photon sources