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Christopher J. Smedley Gencheng Li Andrew S. Barrow Timothy L. Gialelis Marie‐Claire Giel Alessandra Ottonello Yunfei Cheng Seiya Kitamura Dennis W. Wolan K. Barry Sharpless John E. Moses 《Angewandte Chemie (International ed. in English)》2020,59(30):12460-12469
Diversity Oriented Clicking (DOC) is a unified click‐approach for the modular synthesis of lead‐like structures through application of the wide family of click transformations. DOC evolved from the concept of achieving “diversity with ease”, by combining classic C?C π‐bond click chemistry with recent developments in connective SuFEx‐technologies. We showcase 2‐S ubstituted‐A lkynyl‐1‐S ulfonyl F luorides (SASFs) as a new class of connective hub in concert with a diverse selection of click‐cycloaddition processes. Through the selective DOC of SASFs with a range of dipoles and cyclic dienes, we report a diverse click‐library of 173 unique functional molecules in minimal synthetic steps. The SuFExable library comprises 10 discrete heterocyclic core structures derived from 1,3‐ and 1,5‐dipoles; while reaction with cyclic dienes yields several three‐dimensional bicyclic Diels–Alder adducts. Growing the library to 278 discrete compounds through late‐stage modification was made possible through SuFEx click derivatization of the pendant sulfonyl fluoride group in 96 well‐plates—demonstrating the versatility of the DOC approach for the rapid synthesis of diverse functional structures. Screening for function against MRSA (USA300) revealed several lead hits with improved activity over methicillin. 相似文献
33.
We developed a two-stage Ti:sapphire laser system to generate 16 mJ/80 fs laser pulses at a pulse repetition rate of 10 Hz.
The key deriver for the present design is implementing a highly efficient symmetric confocal pre-amplifier and employing a
simple, inexpensive synchronization scheme relying only on a commercial digital delay generator. We characterized the amplified
pulses in spatial, spectral and temporal domains. The laser system was used to investigate various nonlinear optical processes,
and to modify the optical properties of metal and semiconductor surfaces. We are currently building a third amplifier to boost
the laser power to the multi-terawatt range. 相似文献
34.
Tianyi Zhou Wenxiang Ding Mengjia Gaowei Gianluigi De Geronimo Jen Bohon John Smedley Erik Muller 《Journal of synchrotron radiation》2015,22(6):1396-1402
Fabrication and testing of a prototype transmission‐mode pixelated diamond X‐ray detector (pitch size 60–100 µm), designed to simultaneously measure the flux, position and morphology of an X‐ray beam in real time, are described. The pixel density is achieved by lithographically patterning vertical stripes on the front and horizontal stripes on the back of an electronic‐grade chemical vapor deposition single‐crystal diamond. The bias is rotated through the back horizontal stripes and the current is read out on the front vertical stripes at a rate of ~1 kHz, which leads to an image sampling rate of ~30 Hz. This novel signal readout scheme was tested at beamline X28C at the National Synchrotron Light Source (white beam, 5–15 keV) and at beamline G3 at the Cornell High Energy Synchrotron Source (monochromatic beam, 11.3 keV) with incident beam flux ranges from 1.8 × 10?2 to 90 W mm?2. Test results show that the novel detector provides precise beam position (positional noise within 1%) and morphology information (error within 2%), with an additional software‐controlled single channel mode providing accurate flux measurement (fluctuation within 1%). 相似文献
35.
When a shock wave impinges on a surface, it reflects and propagates across the surface at supersonic velocity. The gas is
impulsively accelerated by the passing shock wave. The resulting high-speed flow imparts sufficiently strong forces to particles
on the surface to overcome strong adhesive forces and entrain the surface-bound particles into the gas. This paper describes
an experimental study of the removal of fine particles from a surface by impinging shock waves. The surfaces examined in this
study were glass slides on which uniformly sized (8.3 μm diameter), spherical polystyrene particles had been deposited. Shock
waves were generated in a small, open-ended shock tube at various heights above and impingement angles to the surface. Particle
detachment from the carefully prepared substrates was determined from images of the surfaces recorded before and after shock
impingement. A single shock wave effectively cleaned a large surface area. The centerline length of the cleared region was
used to characterize the efficacy of shock cleaning. A model based upon the far field solution for a point source surface
shock provides a good fit to the clearance length data and yields an estimate to the threshold shock strength for particle
removal.
Received: 13 November 1997/Accepted: 23 April 1998 相似文献
36.
Fabrication of polystyrene hollow microspheres as laser fusion targets by optimized density-matched emulsion technique and characterization 总被引:3,自引:0,他引:3
Inertial confinement fusion, frequently referred to as ICF, inertial fusion, or laser fusion, is a means of producing energy
by imploding small hollow microspheres containing thermonuclear fusion fuel. Polymer microspheres, which are used as fuel
containers, can be produced by solution-based micro-encapsulation technique better known as density-matched emulsion technique. The specifications of these microspheres are very rigorous, and various aspects of the emulsion hydrodynamics associated
with their production are important in controlling the final product. This paper describes about the optimization of various
parameters associated with density-matched emulsion method in order to improve the surface smoothness, wall thickness uniformity
and sphericity of hollow polymer microspheres. These polymer microshells have been successfully fabricated in our lab, with
3–30 μm wall thickness and 50–1600 μm diameters. The sphericity and wall thickness uniformity are better than 99%. Elimination
of vacuoles and high yield rate has been achieved by adopting the step-wise heating of W1/O/W2 emulsion for solvent removal. 相似文献
37.
The conventional type of magnetic well is formed by superposition of two types of magnetic field, axial bumpy field and radial
multipole field. It is used to contain plasma that consists of neutrals, ions and electrons. These particles are in constant
motion in the well and energetic electrons create plasma by violent collisions with neutrals and ions. The confined electrons
are constantly heated by ECR technique in the presence of magnetic field. In this paper it has been shown theoretically that
how the electron motion is influenced in terms of heating, containment and azimuthal uniformity of plasma, by the axial rotation
of the multipole magnetic field [1,2]. Afterwards, the feasibility of achieving a rotating magnetic multipole field is discussed
to some extent. And it is seen that it is not beyond the capability of the scientific community in the present scenario of
the advanced technology. Presently, it can be achieved for lesser field and slightly larger size of the multipole electromagnet
and can be used for improvement of the ECR ion source (ECRIS). 相似文献
38.
We have measured the effect of pressure and temperature on the ionic conductivity of glasses in the system B2O3/Li2O(LiX)2 (X = F, Cl, Br, I), where XB2O3 ? 0.7 and X/O ratio was varied while maintaining a constant Li+ content of X(LiX)2 + Li2O ? 0.3. All glasses exhibited a very small pressure coefficient of conductivity, i.e. ΔV ? 1 cm3 mol?1, which decreased very slightly as the Cl/O ratio increased or as Cl was replaced by Br at constant X/O ratio. The results were compared with the ELectrostatic Strain Energy theory; the results of this comparison lead to the conclusion that for Li+ conduction the electrostatic term is dominant in determining the activation energy for conduction. 相似文献
39.
The contact angle is a critical parameter in liquid interface dynamics ranging from liquid spreading on a solid surface on earth to liquid motion in partially filled containers in space. A refractive tilting-plate technique employing a scanning laser beam is developed to conduct an experimental study of a moving contact line, with the intention of making accurate measurements of the contact angle. The technique shows promise as an accurate and potentially fully automated means to determine the velocity dependence of the contact angle at the intersection of the interface between two transparent fluids with a transparent solid surface. Ray tracing calculations are included to reinforce the measurement concept. The principal experiments were conducted at speeds ranging from 0.05 to 1.00 mm/s, both advancing and receding, using an immiscible liquid pair (nonane/formamide) in contact with glass. The contact angle was found to depend for practical purposes only on the sign of the velocity and not on its magnitude for the range of velocities studied. Other observations revealed a bimodal behavior of the contact line that depends on which liquid first contacts the glass, with resulting drift in the dynamic contact angle with time. 相似文献
40.
Smedley JE Coulter SK Felton EJ Zomlefer KS 《The journal of physical chemistry. A》2008,112(39):9526-9530
Collisional deactivation of the 5d7p (3)D1 state of Ba by noble gases is studied by time- and wavelength-resolved fluorescence techniques. A pulsed, frequency-doubled dye laser at 273.9 nm excites the 5d7p (3)D1 level from the ground state, and fluorescence at 364.1 and 366.6 nm from the 5d7p (3)D1 --> 6s5d (3)D1 and 5d7p (3)D1 --> 6s5d (3)D2 transitions, respectively, is monitored in real time to obtain the deactivation rate constants. At 835 K these rate constants are as follows: He, (1.69 +/- 0.08) x 10(-9) cm(3) s(-1); Ne, (3.93 +/- 0.14) x 10(-10) cm(3) s(-1); Ar, (4.53 +/- 0.15) x 10(-10) cm(3) s(-1); Kr, (4.64 +/- 0.13) x 10(-10) cm(3) s(-1); Xe, (5.59 +/- 0.22) x 10(-10) cm(3) s(-1). From time-resolved 5d7p (3)D1 emission in the absence of noble gas and from the intercepts of the quenching plots, the lifetime of this state is determined to be 100 +/- 1 ns. Using time- and wavelength-resolved Ba emission with a low background pressure of noble gas, radiative lifetimes of several near-resonant states are determined from the exponential rise of the fluorescence signals. These results are as follows: 5d6d (3)D3, 28 +/- 3 ns; 5d7p (3)P1, 46 +/- 2 ns; 5d6d (3)G3, 21.5 +/- 0.8 ns; 5d7p (3)F3, 48 +/- 1 ns. Integrated fluorescence signals are used to infer the relative rate constants for population transfer from the 5d7p (3)D1 state to eleven near-resonant fine structure states. 相似文献