Purcell enhancement of spontaneous emission from quantum cascades inside mirror-grating metal cavities at THz frequencies

Quantum cascade devices processed into double metal cavities with subwavelength thickness and a grating on top are studied at terahertz frequencies. The power extracted from the devices as a function of the device thickness and the grating period is analyzed owing to electrodynamical modeling of dipole emission based on a modal method in multilayer systems. The experimental data thus reveal a strong Purcell enhancement, with Purcell factors up to approximately 50.     

Local Dispersive and Strichartz Estimates for the Schrödinger Operator on the Heisenberg Group

It was proved by Bahouri et al. [9] that the Schrödinger equation on the Heisenberg group $\mathbb{H}^d,$ involving the sublaplacian, is an example of a totally non-dispersive evolution equation: for this reason global dispersive estimates cannot hold. This paper aims at establishing local dispersive estimates on $\mathbb{H}^d$ for the linear Schrödinger equation, by a refined study of the Schrödinger kernel $S_t$ on $\mathbb{H}^d.$ The sharpness of these estimates is discussed through several examples. Our approach, based on the explicit formula of the heat kernel on $\mathbb{H}^d$ derived by Gaveau [19], is achieved by combining complex analysis and Fourier-Heisenberg tools. As a by-product of our results we establish local Strichartz estimates and prove that the kernel $S_t$ concentrates on quantized horizontal hyperplanes of $\mathbb{H}^d.$     

Marfan syndrome in Europe

OBJECTIVES: Marfan syndrome (MFS) is a relatively frequent systemic connective tissue disorder with an important physical morbidity and mortality. The influences of MFS on physical problems, perception of severity, and impact on the quality of life and psychosocial well-being have been studied only limitedly. The aim of this study was to assess the association between the severity derived from the reported symptoms and subjectively experienced severity of MFS (expressed as a global judgment), with special emphasis regarding impact on relationships and pregnancies, psychosocial adjustment, and differences between the seven European countries. METHODS: A questionnaire designed specifically for this study and translated in each of the native languages was sent to 2,080 members of one of the patient support groups in Belgium, Denmark, France, Germany, The Netherlands, Switzerland, and the United Kingdom. 857 MFS patients of 13 years and older completed the questionnaire and were included in the data analysis. RESULTS: Physical impairments were scored by perception of severity of physical symptoms by the patients (physical severity perception score) and by their perception of the influence of MFS on their life (subjective severity score). Main discrepancy between physical severity perception and subjective severity score was the higher percentage of patients scoring in physical severity perception as severe (53.5%) compared to subjectively severe (26.5%). 61% of those who scored on the physical severity score as severely affected were designated as being mildly-moderately affected on subjective scoring. Both severity scores increased significantly with age. Two hundred-twenty women have carried 430 pregnancies (1.95 pregnancies/woman), with cardiovascular complications in 1.6%. Prenatal studies for MFS were rejected by 7.6% of MFS patients of 25 years and older, 33.6% were undecided, and 48.5% favored prenatal diagnosis for MFS if available. A positive general self-image was reported by 91.5% of patients. However, more than 90% stated that MFS had a negative influence on their sexual relationships, which they ascribed to negative perception of their body image. CONCLUSIONS: MFS has significant impact on daily life activities, but the majority of patients come to terms with their condition. Acceptance is mainly determined by subjective severity, and less by physical symptoms as reported by the patients themselves. It is important to stimulate a positive attitude towards MFS.     

Stabilizer‐Guided Inhibition of Protein–Protein Interactions

The discovery of novel protein–protein interaction (PPI) modulators represents one of the great molecular challenges of the modern era. PPIs can be modulated by either inhibitor or stabilizer compounds, which target different though proximal regions of the protein interface. In principle, protein–stabilizer complexes can guide the design of PPI inhibitors (and vice versa). In the present work, we combine X‐ray crystallographic data from both stabilizer and inhibitor co‐crystal complexes of the adapter protein 14‐3‐3 to characterize, down to the atomic scale, inhibitors of the 14‐3‐3/Tau PPI, a potential drug target to treat Alzheimer’s disease. The most potent compound notably inhibited the binding of phosphorylated full‐length Tau to 14‐3‐3 according to NMR spectroscopy studies. Our work sets a precedent for the rational design of PPI inhibitors guided by PPI stabilizer–protein complexes while potentially enabling access to new synthetically tractable stabilizers of 14‐3‐3 and other PPIs.     

MgI2‐Mediated Chemoselective Cleavage of Protecting Groups: An Alternative to Conventional Deprotection Methodologies

The scope of MgI₂ as a valuable tool for quantitative and mild chemoselective cleavage of protecting groups is described here. This novel synthetic approach expands the use of protecting groups, widens the concept of orthogonality in synthetic processes, and offers a facile opportunity to release compounds from solid supports.     

Method validation in analytical sciences: discussions on current practice and future challenges

Accreditation and Quality Assurance - Eurachem held a workshop on method validation in analytical sciences in Gent, Belgium, on 9–10 May 2016. A summary of the working group discussions is...     

An experimental design based strategy to optimize a capillary electrophoresis method for the separation of 19 polycyclic aromatic hydrocarbons

Because of their high toxicity, international regulatory institutions recommend monitoring specific polycyclic aromatic hydrocarbons (PAHs) in environmental and food samples. A fast, selective and sensitive method is therefore required for their quantitation in such complex samples. This article deals with the optimization, based on an experimental design strategy, of a cyclodextrin (CD) modified capillary zone electrophoresis separation method for the simultaneous separation of 19 PAHs listed as priority pollutants. First, using a central composite design, the normalized peak-start and peak-end times were modelled as functions of the factors that most affect PAH electrophoretic behavior: the concentrations of the anionic sulfobutylether-β-CD and neutral methyl-β-CD, and the percentage of MeOH in the background electrolyte. Then, to circumvent computational difficulties resulting from the changes in migration order likely to occur while varying experimental conditions, an original approach based on the systematic evaluation of the time intervals between all the possible pairs of peaks was used. Finally, a desirability analysis based on the smallest time interval between two consecutive peaks and on the overall analysis time, allowed us to achieve, for the first time in CE, full resolution of all 19 PAHs in less than 18 min. Using this optimized capillary electrophoresis method, a vegetable oil was successfully analyzed, proving its suitability for real complex sample analysis.     

New approach in the synthesis of M6G

Morphine-6-glucuronide (M6G) is the primarily active metabolite of morphine, produced endogenously by the UGT enzyme, which displays analgesic activity. For this reason, M6G is a promising drug candidate for the treatment of severe pain. We described herein a new, efficient and scalable synthesis of M6G using dimorphinic derivatives. This preparation of M6G could be performed on multigram scale with good yield and high purity.     

Freeze-fracture TEM imaging of robust order in swollen phases of amphiphilic diblock copolymers

We report on the structures exhibited by two different diblock poly(styrene)-b-poly(acrylic acid) (PS-b-PAA) copolymers in water, a selective solvent. Using a combination of X-ray scattering and freeze fracture-transmission electron microscopy (FF-TEM), we show that these structures can be widely swollen while retaining their initial morphology and a high degree of long-range order. The analysis of the FF-TEM pictures also evidences the presence of water crystallites of regular size and shape within the confined water domains. We relate the growth of these crystallites to the high local ionic strength of the water swelling the PAA brushes. Moreover, the confinement of the crystallites growth shows that the swollen phases have a very robust structure, potentially useful for confining colloidal particles.