Preparation of 3-azetidinols with non-bulky 1-alkyl substituents

Cyclization of either the tetrahydropyranyl or trimethylsilyl ether of 1-(alkylamino)-3-chloro-2-propanols 1 followed by cleavage of the azetidinyl ether provides a general method for the preparation of 1-alkyl-3-azetidinols. Unhindered amines provide a more facile preparation of derivatives of 1 , or its ethers, than do hindered amines, while hindered derivatives of 1 undergo more facile ring closure.     

Simulations of radiative effects on the Rayleigh–Taylor instability using the CRASH code

Future experiments at the National Ignition Facility will be able to generate diagnosable Rayleigh–Taylor instability growth in the presence of locally generated, high radiation fluxes. This interplay of radiative energy transfer and hydrodynamic instability is relevant to many astrophysical systems, such as core-collapse red supergiant supernovae. Previous simulations of high-energy-density Rayleigh–Taylor instabilities in the presence of a hot environment near a radiative shock demonstrate behavior that differs from that found in non-radiative cases. However, these simulations considered only 1D or single wavelength cases. Here we report simulations of an entire experimental system using the CRASH code. These simulations lead to modified predictions, attributed to the effects of radial energy losses.     

Dual‐Modal Magnetic Resonance/Fluorescent Zinc Probes for Pancreatic β‐Cell Mass Imaging

Despite the contribution of changes in pancreatic β‐cell mass to the development of all forms of diabetes mellitus, few robust approaches currently exist to monitor these changes prospectively in vivo. Although magnetic‐resonance imaging (MRI) provides a potentially useful technique, targeting MRI‐active probes to the β cell has proved challenging. Zinc ions are highly concentrated in the secretory granule, but they are relatively less abundant in the exocrine pancreas and in other tissues. We have therefore developed functional dual‐modal probes based on transition‐metal chelates capable of binding zinc. The first of these, Gd ?1 , binds Zn^II directly by means of an amidoquinoline moiety (AQA), thus causing a large ratiometric Stokes shift in the fluorescence from λ_em=410 to 500 nm with an increase in relaxivity from r₁=4.2 up to 4.9 mM ^?1 s^?1. The probe is efficiently accumulated into secretory granules in β‐cell‐derived lines and isolated islets, but more poorly by non‐endocrine cells, and leads to a reduction in T₁ in human islets. In vivo murine studies of Gd ?1 have shown accumulation of the probe in the pancreas with increased signal intensity over 140 minutes.     

Simulations of laser experiments of radiative and non-radiative shocks

The Center for Radiative Shock Hydrodynamics (CRASH) at the University of Michigan was established to study the properties of radiative shocks using both numerical simulation and shock-tube experiments on the Omega Laser at the University of Rochester. The laser accelerates a thin Be disk, which acts like a piston, driving a shock with an initial propagation velocity of 200 km/s into a tube filled with Xe. Analytic estimates indicate that a shock propagating with a velocity greater than about 60 km/s through Xe under these conditions should be strongly radiative. This paper discusses numerical simulations of a proposed modification to this experiment that produces a non-radiative shock. Comparison of the radiative and non-radiative cases provides an excellent opportunity for assessing the effects of radiation on shock structure and flow morphology. For the non-radiative case, the initial shock speed is reduced to 20 km/s by increasing the thickness of the Be disk and by decreasing the energy of the laser. Two-dimensional simulations of targets with cylindrical shock tubes and three-dimensional simulations of more complex targets with elliptical shock tubes are described. In addition, the effect of the shock speed on the cross-sectional area of the tube is discussed.     

Interactive System for Similarity-Based Inspection and Assessment of the Well-Being of mHealth Users

Recent digitization technologies empower mHealth users to conveniently record their Ecological Momentary Assessments (EMA) through web applications, smartphones, and wearable devices. These recordings can help clinicians understand how the users’ condition changes, but appropriate learning and visualization mechanisms are required for this purpose. We propose a web-based visual analytics tool, which processes clinical data as well as EMAs that were recorded through a mHealth application. The goals we pursue are (1) to predict the condition of the user in the near and the far future, while also identifying the clinical data that mostly contribute to EMA predictions, (2) to identify users with outlier EMA, and (3) to show to what extent the EMAs of a user are in line with or diverge from those users similar to him/her. We report our findings based on a pilot study on patient empowerment, involving tinnitus patients who recorded EMAs with the mHealth app TinnitusTips. To validate our method, we also derived synthetic data from the same pilot study. Based on this setting, results for different use cases are reported.     

Complete coverage of reduced graphene oxide on silicon dioxide substrates

Reduced graphene oxide(RGO) has the advantage of an aqueous and industrial-scale production route. No other approaches can rival the RGO field effect transistor platform in terms of cost(相似文献   

Mild conditions for the synthesis of functionalized pyrrolidines via Pd-catalyzed carboamination reactions

[reaction: see text] The palladium-catalyzed carboamination of N-protected gamma-aminoalkenes with aryl bromides and triflates has been achieved under new, mild reaction conditions using the weak base Cs(2)CO(3) in dioxane solvent. These reactions tolerate a wide variety of functional groups, including enolizable ketones, nitro groups, methyl esters, and acetates, which are not compatible with previously described conditions.     

Palladium-catalyzed synthesis of cyclopentane-fused benzocyclobutenes via tandem directed carbopalladation/C-H bond functionalization

A new Pd-catalyzed reaction for the stereoselective synthesis of cyclopentane-fused benzocyclobutenes is described. These transformations likely proceed via carbamate-directed carbopalladation followed by intramolecular C-H activation of an alkylpalladium intermediate. The mechanistic relationship between these transformations and Pd-catalyzed reactions of gamma-(n-Boc-amino)alkenes with aryl bromides that afford pyrrolidines is discussed. Differences in reactivity between Pd-amino and Pd-amido complexes appear to play a key role in the outcome of these transformations.     

Uncertainty quantification in LES of channel flow

In this paper, we present a Bayesian framework for estimating joint densities for large eddy simulation (LES) sub‐grid scale model parameters based on canonical forced isotropic turbulence direct numerical simulation (DNS) data. The framework accounts for noise in the independent variables, and we present alternative formulations for accounting for discrepancies between model and data. To generate probability densities for flow characteristics, posterior densities for sub‐grid scale model parameters are propagated forward through LES of channel flow and compared with DNS data. Synthesis of the calibration and prediction results demonstrates that model parameters have an explicit filter width dependence and are highly correlated. Discrepancies between DNS and calibrated LES results point to additional model form inadequacies that need to be accounted for. Copyright © 2016 John Wiley & Sons, Ltd.     

Simulating radiative shocks with the CRASH laser package

We present the latest improvements in the Center for Radiative Shock Hydrodynamics (CRASH) code, a parallel block-adaptive-mesh Eulerian code for simulating high-energy-density plasmas. The implementation can solve for radiation models with either a gray or a multigroup method in the flux-limited-diffusion approximation. The electrons and ions are allowed to be out of temperature equilibrium and flux-limited electron thermal heat conduction is included. We have recently implemented a CRASH laser package with 3-D ray tracing, resulting in improved energy deposition evaluation. New, more accurate opacity models are available which significantly improve radiation transport in materials like xenon. In addition, the HYPRE preconditioner has been added to improve the radiation implicit solver. With this updated version of the CRASH code we study radiative shock tube problems. In our set-up, a 1 ns, 3.8 kJ laser pulse irradiates a 20 micron beryllium disk, driving a shock into a xenon-filled plastic tube. The electrons emit radiation in the shocked xenon. This radiation preheats the unshocked xenon. Photons traveling ahead of the shock will also interact with the plastic tube, heat it, and in turn this can drive another shock off the wall into the xenon.